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The mechanisms for chaos terrain formation on Europa have long been a source of debate in the scientific community. There exist numerous theoretical and numerical models for chaos formation, but to date there has been a lack of quantifiable observations that can be used to constrain models and permit comparison to the outputs of these chaos models. Here, we use mapping and statistical analysis to develop a quantitative description of chaos terrain and their observed morphologies. For nine chaos features, we map every block, or region of pre-existing terrain within disrupted matrix. We demonstrate that chaos terrains follow a continuous spectrum of morphologies between two endmembers, platy and knobby. We find that any given chaos terrain's morphology can be quantified by means of the linearized exponential slope of its cumulative block area distribution. This quantitative metric provides a new diagnostic parameter in future studies of chaos terrain formation and comparison.

MSP is a serum protein belonging to the plasminogen-related kringle domain protein family. In addition to macrophages, epithelial cells are also MSP targets. MSP is a multifunctional factor regulating cell adhesion and motility, growth and survival. MSP mediates its biological activities by activating a transmembrane receptor tyrosine kinase called RON in humans or SKT in mice. MSP can protect epithelial cells from apoptosis by activating two independent signals in the PI3-K/AKT or the MAPK pathway. The MAPK pathway mediates the MSP antiapoptotic effect only if additional signaling pathways are activated through adhesion. This indicates that MSP receptors and integrins, the receptors mediating cell-matrix-dependent adhesion, can collaborate in promotion of cell survival. This adhesion-dependent pathway, which is essential for the MAPK-mediated anti-apoptotic effect, remains to be identified. A hypothesis that Stat3 might represent a key component of the adhesion-induced anti-apoptotic pathway is presented in this review.

Macrophage-stimulating protein (MSP), originally identified as an inducer of murine resident macrophage responsiveness to chemoattractants, is a ligand for human RON/murine STK receptor protein tyrosine kinases. Since STK was cloned from populations enriched for hematopoietic stem cells, we initiated studies on the effects of MSP on colony formation by granulocyte-macrophage (CFU-GM), erythroid (BFU-E), and multipotential (CFU-GEMM) myeloid progenitor cells. MSP alone had no colony stimulating activity. However, MSP caused about a 50% suppression of CFU-GM colony formation induced by synergistic combinations of SLF or Flt-L plus GM-CSF, G-CSF, or IL-3 and of BFU-E and CFU-GEMM colonies induced by SLF or Flt3-L plus Epo or Epo and IL-3. In contrast, MSP had no effect on progenitors stimulated by one growth factor. MSP also suppressed colony formation by stimulated cord blood progenitors, but only after preinduction to a rapidly cycling state. It was previously reported that several members of the chemokine family synergistically suppress myeloid progenitor proliferation. Likewise, synergistic suppression was observed when MSP was paired with VEGF, MIP-1 alpha, IL-8, PF4, MCP-1, IP-10, or ENA-78, or when VEGF was paired with the chemokines; and the required MSP concentration was more than 100-fold less than for MSP alone. Additionally, MSP or VEGF inhibited proliferation of the human myeloid growth factor-dependent cell line, M07e, but a sustained effect required multiple additions over time. At the least, some of the MSP suppressive effects on myeloid progenitors, as assessed on single isolated CD34 marrow cells, appeared to be directly on the progenitors; sustained additions of MSP were required to see this effect. The suppressive action of MSP and its synergism with proteins of the chemokine family may be of relevance to regulation of blood cell production.

Macrophage-stimulating protein (MSP) induces mouse resident peritoneal macrophages to become responsive to the chemoattractant C5a and to ingest C3bi-coated erythrocytes. We now show that MSP action is not limited to complement-induced responses, because it also induced responsiveness to the noncomplement chemoattractant casein. In addition to stimulating responsiveness to attractants, MSP functioned alone as a chemoattractant for resident peritoneal macrophages, with an optimal concentration of approximately 0.2 nM. A critical difference between MSP and C5a is that resident macrophages did not migrate to C5a without an additional stimulus such as MSP in the cell suspension, whereas macrophages suspended in medium alone migrated to MSP in the attractant well. Thus, in contrast to C5a, MSP seems capable of a dual role, both activator and attractant. MSP had no effect on responsiveness of mouse peritoneal exudate macrophages to C5a; nor could it attract exudate macrophages or human blood monocytes. Absorption studies showed that resident macrophages have a receptor for MSP, but exudate macrophages do not. In view of these findings, it seems that the biological role of MSP is not as a recruiter of blood monocytes to sites of inflammation, but as an activator of mature macrophages. The MSP-induced activated state for responsiveness to C5a or C3bi was transient, and decayed at a first order rate with a t 1/2 of approximately 1 h. This is a new example of the transience of activation induced in macrophages by proinflammatory stimuli.

We recently found that normal human sera contain IgG antibodies against two chemoattractants, neutrophil attractant protein-1 (NAP-1/IL-8) and monocyte chemoattractant protein-1 (MCP-1), as well as immune complexes of these proteins. Intravenously administered LPS was reported to cause a sharp rise in serum NAP-1 concentration. Our study was designed to determine if LPS also caused an increase in MCP-1 and to measure associated changes in concentrations of antibody and immune complex. LPS caused a rise to peak within 2 to 3 h in serum concentrations of free NAP-1 and MCP-1, followed by an almost equally rapid fall toward base-line levels by about 5 h postinjection. MCP-1 concentration in sera from the 11 subjects rose to a peak of 330 +/- 52 pM. The peak value for NAP-1 was 80 +/- 11 pM. In 10 of the 11 subjects, free IgG autoantibody to MCP-1 decreased from a mean pre-LPS value of 1820 +/- 660 pM to a mean low of 53% of the respective initial values. Corresponding data for IgG anti-NAP-1 were a pre-LPS concentration of 216 +/- 7 pM, which decreased to a mean low of 44% of the respective initial values. The finding in some subjects of a rapid rise in free antibody after the nadir suggests the possibility of acute regulation of autoantibody secretion rates. Although the results suggested that LPS-induced chemoattractant combined with free antibody, serum concentrations of MCP-1-IgG or NAP-1-IgG did not increase, which points to an as yet unknown mechanism for trapping and elimination of the immune complexes.

We developed five different hybridoma cell lines that produced mAb against human monocyte chemoattractant protein-1 (MCP-1). The subclass of all five antibodies was IgG1. All five mAb formed complexes with metabolically labeled MCP-1 that could be demonstrated by immunoprecipitation. The antibodies were specific for MCP-1. They did not cross-react by immunoprecipitation with structurally related host defense cytokines present in metabolically labeled PHA- or LPS-stimulated mononuclear cell culture fluids, nor did they cross-react in a direct ELISA with neutrophil attractant/activation protein-1, with crude platelet lysate proteins, or with pure platelet proteins that have amino acids sequences similar to that of MCP-1. The mAb also reacted with rMCP-1 expressed in Escherichia coli, suggesting that they recognize protein structure rather than the glycosylated portion of human MCP-1. When the mAb were mixed with MCP-1, the monocyte chemotactic response to MCP-1 was inhibited. A sandwich ELISA was developed to detect MCP-1 in biologic fluids containing relatively high concentrations of other proteins. The sensitivity was 300 pg/ml, or 30 pg/ELISA well. An anti-MCP-1 mAb column was used in an improved method of MCP-1 purification. Approximately 240 micrograms of MCP-1 were purified from 5 liters of FCS-containing U-105MG cell culture supernatant. The yield was at least 60%. In addition to two forms of MCP-1 reported previously by us, two more forms of MCP-1 were found in a mixture of culture supernatants of PHA- and LPS-stimulated human PBMC.

The binding of human monocyte chemoattractant protein-1 (MCP-1) to human monocytes was studied. MCP-1 was radioiodinated with Iodo-beads (Pierce Chemical Co., Rockford, IL) without significant loss of biologic activity. 125I-MCP-1 binding to PBMC occurred within 5 min at 0 degrees C and the binding was inhibited by unlabeled MCP-1 dose dependently but not by neutrophil attractant/activation protein-1 or FMLP. 125I-MCP-1 bound to monocytes; no significant binding to either neutrophils or lymphocytes was observed. Scatchard plot analysis indicated that monocytes had a minimum of 1700 +/- 600 binding sites per cell with a Kd of 1.9 +/- 0.2 x 10(-9) M. For analysis of binding by flow cytometry, MCP-1 was biotinylated. In contrast to radioiodination, biotinylation resulted in loss of activity; potency was 10-fold less, but the efficacy was retained. Detection by flow cytometry of bound biotinylated MCP-1 with avidin-FITC confirmed results obtained with 125I-MCP-1. Biotinylated MCP-1 bound to monocytes but not to lymphocytes; and the binding was inhibited by a 100-fold excess of unlabeled MCP-1.

Neutrophil attractant/activation protein-1 (NAP-1) was previously shown to attract human neutrophils, but not monocytes. The purpose of this study was to determine if NAP-1 interacted with other types of blood leukocytes. In addition to its chemotactic activity for neutrophils, NAP-1 induced chemotactic responses by T lymphocytes and basophils. Chemotactic potency (10(-8) M for an optimal response) was the same for all three cell types. However, NAP-1 caused a chemotactic response in excess of random migration of 7% or 16% of basophils (depending on the medium used) and only 9% of T lymphocytes, in contrast to 30% of neutrophils. This agonist was not chemotactic for partially purified normal human eosinophils. The symmetrical histogram obtained by flow cytometry of neutrophils equilibrated at 0 degree C with fluoresceinated NAP-1 indicates that all neutrophils bound the ligand. A dose-response curve plateau, and inhibition of binding of NAP-1-FITC by unlabeled ligand are evidence for saturable binding to receptors, estimated to be 7000 per cell. Our results suggest that, for induction of an acute inflammatory response, the quantitatively significant action of NAP-1 is on neutrophils.

Background AAK is a key mitotic regulator overexpressed/amplified in a variety of tumor types including prostate cancer. MLN8237 is an oral, selective AAK inhibitor. Here we report emerging data from the first clinical study of MLN8237 in combination with docetaxel in pts with solid tumors or CRPC. Methods Pts aged ≥18 y with ≤3 prior myelosuppressive chemotherapy regimens who were candidates for docetaxel received MLN8237 BID (days 1–5 or 1–7) in 3 + 3 dosing cohorts plus docetaxel on day 1 in 21-d cycles. Primary objectives were safety/tolerability and to determine a recommended phase 2 dose/schedule (RP2D); secondary objectives were pharmacokinetics (PK) and antitumor activity (RECIST v1.1 and/or PSA response by PCWG2). Results 22 pts in 5 dose cohorts received a median of 5 cycles (range 1–17); 9 pts remain on therapy. Median age was 63 y (36–87), 82% were male, and 14 had CRPC. 8 pts reported dose-limiting toxicities including G4 neutropenia >7 days (n = 5) and G3/4 febrile neutropenia (n = 3). MTD has not yet been reached. 21 pts reported drug-related AEs; G ≥ 3 in 20 pts, including neutropenia (86%), leukopenia (27%), and febrile neutropenia (23%). 11 pts had serious AEs and 3 discontinued due to AEs. There were 2 on-study deaths (due to disease progression). Steady-state systemic exposure of MLN8237 increased in an approx. dose proportional manner over 10–30 mg BID when administered with docetaxel 75 mg/m (n = 18). There was no consistent effect of MLN8237 dose on docetaxel exposure (n = 19). Of 20 response-evaluable pts, 3 with CRPC achieved PR plus a >50% decrease in PSA and 7 had stable disease including 3 pts who also had a >50% decrease in PSA; 1 pt with bladder cancer had a PR. Conclusions Myelosuppressive G ≥ 3 AEs were common, but 10 of 22 pts remained on study for ≥6 cycles. PK data from the expansion cohort are pending to support definitive conclusions regarding drug-drug interaction between docetaxel and MLN8237. Emerging data suggest this combination may have preliminary antitumor activity in pts with solid tumors/CRPC. Dose escalation/modification is ongoing to determine RP2D. Disclosure N.M. Hahn: Research Support to institution: Merck, Dendreon, Sanofi, Millennium, Exelexis, Novartis, Bristol-Myers Squibb, Celgene Consultant: Sanofi, Celgene Speakers Bureau Honoraria: Sanofi, Janssen Biotech, C. Higano: Amgen, Bayer, Dendreon, GTx, MPI, AZ, Pfizer, Cell Ther., Centocor, Perceptive Inform., Sanofi, TEVA, BMS, Aragon, Cell Genesys, Exelixis, Genentech, GSK, ImClone, OncoGenex, Mediv., Clin. Care Ops, Curatio, Medscape, RBC Capital Mkts Corp., Cougar, Endo, X. Zhou: Employment (Millennium Pharmaceuticals, Inc.), B. Zhang: Employment: Millennium Pharmaceuticals, Inc., E.J. Leonard: Employment (Millennium Pharmaceuticals, Inc.) Ownership interest (Millennium Pharmaceuticals, Inc.), E. Benaim: Employment (Millennium Pharmaceuticals, Inc.). All other authors have declared no conflicts of interest.

MSP is a serum protein belonging to the plasminogen-related kringle domain protein family. In addition to macrophages, epithelial cells are also MSP targets. MSP is a multifunctional factor regulating cell adhesion and motility, growth and survival. MSP mediates its biological activities by activating a transmembrane receptor tyrosine kinase called RON in humans or SKT in mice. MSP can protect epithelial cells from apoptosis by activating two independent signals in the PI3-K/AKT or the MAPK pathway. The MAPK pathway mediates the MSP antiapoptotic effect only if additional signaling pathways are activated through adhesion. This indicates that MSP receptors and integrins, the receptors mediating cell-matrix-dependent adhesion, can collaborate in promotion of cell survival. This adhesion-dependent pathway, which is essential for the MAPK-mediated anti-apoptotic effect, remains to be identified. A hypothesis that Stat3 might represent a key component of the adhesion-induced anti-apoptotic pathway is presented in this review.

RON is a transmembrane receptor tyrosine kinase that mediates biological activities of Macrophage Stimulating Protein (MSP). MSP is a multifunctional factor regulating cell adhesion, motility, growth and survival. MSP binding to RON causes receptor tyrosine phosphorylation leading to up-regulation of RON catalytic activity and subsequent activation of downstream signaling molecules. Recent studies show that RON is spatially and functionally associated with other transmembrane molecules including adhesion receptors integrins and cadherins, and cytokine and growth factor receptors IL-3 betac, EPOR and MET. For example, MSP-induced cell shape change is mediated via RON-activated IL-3 betac receptor. Activation of integrins causes MSP-independent RON phosphorylation, and the integrin/RON collaboration regulates cell survival. Thus, RON can be activated without MSP by ligand stimulation of RON-associated receptors, and MSP-activated RON can cause ligand-independent activation of RON-associated receptors. As a result of the receptor cross-activation RON-specific pathways become a part of a signal transduction network of other receptors, and conversely signaling pathways activated by other receptors can be used by RON. This receptor collaboration extends the spectrum of cellular responses generated by MSP and by putative ligands of RON-associated receptors. However signaling pathways involved in the receptor cross-talk and underlying activation mechanisms remain to be investigated. The purpose of this review is to summarize data and to discuss a role of cross-talk between RON and other transmembrane receptors.

Macrophage-stimulating protein (MSP) and hepatocyte growth factor/scatter factor (HGF/SF) are plasminogen-related growth and motility factors that interact with cell-surface protein tyrosine kinase receptors. Each one is a heterodimeric protein comprising a disulfide-linked alpha chain and a serine protease-like beta chain. Despite structural similarities between MSP and HGF, the primary receptor binding site is located on the alpha chain of HGF/SF but on the beta chain of MSP. To obtain insight into the structural basis for MSP beta chain binding, beta chain structure was modeled from coordinates of an existing model of the HGF beta chain. The model revealed that the region corresponding to the S1 specificity pocket in trypsin is filled by the Asn(682)/Glu(648) interacting pair, leaving a shallow cavity for possible beta chain interaction with the receptor. Mutants in this region were created, and their binding characteristics were determined. A double mutation of Asn(682)/Glu(648) caused diminished binding of the beta chain to the MSP receptor, and a single mutation of neighboring Arg(683) completely abolished binding. Thus, this region of the molecule is critical for binding. We also found that at equimolar concentrations of free alpha and beta chains, alpha chain binding to receptor was detectable, at levels considerably lower than beta chain binding. The EC(50) values determined by quantitative enzyme-linked immunosorbent assay are 0.25 and 16.9 nM for beta and alpha chain, respectively. The data suggest that MSP has two independent binding sites with high and low affinities located in beta and alpha chain, respectively, and that the two sites together mediate receptor dimerization and subsequent activation.

Hepatocyte growth factor/scatter factor (HGF/SF) and macrophage stimulating protein (MSP) are plasminogen-related kringle proteins that lost serine protease domain enzymatic activity and became ligands for cell surface tyrosine kinase receptors. They are activated by cleavage to disulfide-linked alphabeta chains. Surprisingly, despite structural similarities, the high affinity receptor binding regions of the two proteins are different: alpha chain for HGF, and beta chain for MSP. We propose that after cleavage exposes a beta chain binding site (high affinity for MSP, low affinity for HGF), monomeric ligand induces receptor dimerization and activation via alpha and beta chain binding sites of different affinity.

Macrophage-stimulating protein (MSP; also known as HGF-like protein [HGFl]) is a 78 kDa plasma protein that is secreted by the liver into the circulation as single-chain, biologically inactive pro-MSP. The presence of conserved triple disulfide loops (kringles) places pro-MSP in a family of coagulation system serine protease zymogens that are activated by proteolytic cleavage. Although pro-MSP has lost enzymic activity, it has retained the activation mechanism, in that proteolytic cleavage at a single site yields biologically active disulfide-linked alpha beta-chain heterodimeric MSP. The MSP receptor is a transmembrane protein tyrosine kinase. MSP causes phosphorylation of the receptor cytoplasmic domain, association of phosphatidylinositol (PI)-3 kinase with the receptor, and phosphorylation of receptor-bound PI-3 kinase. Inhibition of PI-3 kinase by wortmannin prevents MSP action on cells. MSP stimulates motility of murine resident peritoneal macrophages. However, it does not act on exudate macrophages or blood monocytes, since these earlier maturational stages of the lineage do not express the receptor. MSP also stimulates keratinocyte cell lines, causing either chemotactic responses or increased cell numbers in culture. We suggest that pro-MSP diffuses into local tissue sites, where proteolytic cleavage to MSP results in stimulation of keratinocytes and macrophages. It possibly plays a role in tissue injury or wound healing.

Macrophage stimulating protein (MSP) is a ligand for the RON receptor protein tyrosine kinase. Activation of RON in murine resident macrophages results in cell shape change and migration. We studied cell movement induced by MSP in different types of human epithelial cells and the possible role of phosphatidylinositol-3 (PI-3) kinase in RON-mediated signal transduction. We observed specific and saturable binding of 125I-MSP to RON on several epithelial cell lines. In addition to activation and phosphorylation of RON, MSP also induced tyrosine phosphorylation of the PI-3 kinase p85 subunit in a time-dependent manner, with a peak at 15 min. Moreover, phosphorylated RON formed a complex with PI-3 kinase in both HK-NOC keratinocyte and RON cDNA-transfected MDCK cells. An in vitro protein interaction assay confirmed that PI-3 kinase from a lysate of MSP-activated cells bound to pure RON protein. MSP, at a concentration range of 1 to 5 nM, induced migration of three epithelial cell lines. This effect was inhibited by wortmannin, a specific inhibitor for PI-3 kinase, with an IC50 of 10 nM. MSP-induced shape change in murine resident peritoneal macrophages was also abolished by wortmannin. These data suggest that activation of PI-3 kinase is required for MSP-induced epithelial cell migration. The stimulation by MSP of epithelial cell movement may have implications for tissue repair, wound healing, and tumor metastasis.

Background Androgen deprivation therapy (ADT) is the standard treatment of hormone-sensitive metastatic prostate cancer (HSMPC). We performed a phase III multicentre trial to compare ADT alone with ADT plus docetaxel (D) in HNMPC. Methods Patients (pts) with HSMPC were randomly assigned to either arm A (ADT + D: 75mg/m q3w, up to 9 cycles) or arm B (ADT). The primary endpoint was overall survival (OS). The planned number of pts was 378 to detect an improvement in OS with a hazard ratio (HR) of 0.62, a power of 80% and an alpha risk of 0.05 (two-sided test). Secondary endpoints were biological progression-free survival (PFS) and clinical PFS. Data on toxicity and quality of life have been previously presented. Results From October 2004 to December 2008, 385pts were included. Baseline characteristics were well balanced between the two arms. Median age was 63 years (43-84), median PSA was 26.4 ng/ml (0.1-11900), Gleason score was ≥ 8 in 57%. Prognostic classification was as follows: good prognosis (49%), intermediate (29%) and poor (22%). The majority of pts had metastases at the time of diagnosis (72%), 28% developed metastases after local treatment failure. Median number of D cycles was 8 (range 0-9). The median follow-up was 50 months (mo) [95%CI: 49-54]. At 6 mo, a higher PSA response (≥ 50%) in arm A (94% vs 85%, p = 0.0096) and a higher PSA progression (≥ 25%) in arm B (10% vs 1%, p = 0.0015) were observed. Biological PFS was significantly longer in arm A: 22.9 vs 12.9 mo, HR; 0.72 [95%CI: 0.57-0.91] (p = 0.005). Clinical PFS was increase in arm A: 23.46 vs 15.44 mo, HR: 0.75 [95CI: 0.59-0.94] (0.015). OS was not significantly different (median: 58.9 mo in arm A and 54.2 mo in arm B, HR: 1.01 [95%CI: 0.75-1.36]. The median OS for each prognostic group was 69.1 [95%CI: 60.9-NR], 46.5 [95%CI: 37.7-NR] and 36.6 [95%CI9: 28.5-58.9] mo respectively in the good, intermediate, and poor prognosis groups (p = 0.001), with no difference between the two arms. At the cut-off time, 65% of pts from the ADT arm had received docetaxel since they developed castrate-resistant prostate cancer. Conclusion Combining docetaxel and ADT improves PFS over ADT alone in pts with HSMPC. However, no difference in OS was observed between the two arms. Disclosure G. Gravis: I have expert testimony to disclose: Sanofi Aventis, uncompensated. K. Fizazi: Participation to advisory boards and speaker for Sanofi-Aventis. F. Joly Lobbedez: advisory board/board of directors position: Sanofi, Roche, Pfizer, Novartis, Ferring; compensated consultant relationship: Roche, Novartis; honoraria: Sanofi, Roche, Pfizer, Novartis, Ferring, Ipsen,Takeda; travel remuneration: ASCO by Novartis, ESMO by Janssen. S. Oudard: I have an advisory relationship and honoraria to disclose: Pfizer Oncology, Bayer-Schering Pharma, Hoffman La Roche, Glaxo SmithKline, Novartis Pharma, Sanofi Aventis. D. Pouessel: Consultant role and honoraria: Sanofi, P. Beuzeboc: Presentations: Avantis, All other authors have declared no conflicts of interest.

Human serum macrophage-stimulating protein (MSP) is a disulfide-linked heterodimer that induces motile and phagocytic activity of mouse resident peritoneal macrophages. In this work, we found that MSP blocked the increase in macrophage nitric oxide synthase mRNA, as well as the associated increase in nitric oxide production, that occurred in response to several stimuli. These included bacterial products and mammalian cytokines: endotoxin, and interferon-gamma plus endotoxin, interleukin-2, or tumor necrosis factor-alpha. The inhibition by MSP of induction of nitric oxide synthase mRNA and nitric oxide secretion was concentration-dependent. The concentration of MSP that caused maximal inhibition of nitric oxide production was comparable with the optimum for stimulation of macrophage motile and phagocytic activity. Time course studies showed that nitrite was first detected in culture fluid about 8 h after endotoxin stimulation, and it accumulated at a linear rate during the ensuing 16 h. Inhibition by MSP occurred during the 8-h lipopolysaccharide (LPS) induction period; inhibition was maximal when MSP and LPS were added together and decreased progressively to no inhibition as the interval between LPS and MSP addition increased to 11 h.

Macrophage-stimulating protein (MSP) induces mouse resident peritoneal macrophages to become responsive to the chemoattractant C5a and to ingest C3bi-coated erythrocytes. We now show that MSP action is not limited to complement-induced responses, because it also induced responsiveness to the noncomplement chemoattractant casein. In addition to stimulating responsiveness to attractants, MSP functioned alone as a chemoattractant for resident peritoneal macrophages, with an optimal concentration of approximately 0.2 nM. A critical difference between MSP and C5a is that resident macrophages did not migrate to C5a without an additional stimulus such as MSP in the cell suspension, whereas macrophages suspended in medium alone migrated to MSP in the attractant well. Thus, in contrast to C5a, MSP seems capable of a dual role, both activator and attractant. MSP had no effect on responsiveness of mouse peritoneal exudate macrophages to C5a; nor could it attract exudate macrophages or human blood monocytes. Absorption studies showed that resident macrophages have a receptor for MSP, but exudate macrophages do not. In view of these findings, it seems that the biological role of MSP is not as a recruiter of blood monocytes to sites of inflammation, but as an activator of mature macrophages. The MSP-induced activated state for responsiveness to C5a or C3bi was transient, and decayed at a first order rate with a t 1/2 of approximately 1 h. This is a new example of the transience of activation induced in macrophages by proinflammatory stimuli.

Human serum macrophage stimulating protein (MSP) is a disulfide-linked heterodimer that induces motile and phagocytic activity of mouse resident peritoneal macrophages. It is a member of the family of kringle proteins, which typically exist in extracellular fluid as single chain precursors that are activated by proteolytic cleavage. In this work, we expressed [35S]cysteine-labeled recombinant pro-MSP in MSP cDNA-transfected Chinese hamster ovary cells and studied proteolytic processing of pro-MSP and the requirement of cleavage for biological activity. In media containing heat-inactivated fetal bovine serum, the protein was secreted as single chain pro-MSP, which was cleaved over a period of hours to the mature heterodimer. Cleavage was prevented by serine protease inhibitors such as leupeptin or aprotinin; it did not occur if cells were cultured in serum-free medium. Nanomolar concentrations of coagulation proteases kallikrein, factor XIIa or factor XIa cleaved pro-MSP to MSP within 30 min. Pro-MSP had no biological activity. After cleavage by kallikrein, biological activity was quantitatively comparable to that of natural MSP isolated from human plasma. These results support our hypothesis that MSP circulates as the biologically inactive precursor and can be activated by enzymes of the intrinsic coagulation cascade.

We recently found that normal human sera contain IgG antibodies against two chemoattractants, neutrophil attractant protein-1 (NAP-1/IL-8) and monocyte chemoattractant protein-1 (MCP-1), as well as immune complexes of these proteins. Intravenously administered LPS was reported to cause a sharp rise in serum NAP-1 concentration. Our study was designed to determine if LPS also caused an increase in MCP-1 and to measure associated changes in concentrations of antibody and immune complex. LPS caused a rise to peak within 2 to 3 h in serum concentrations of free NAP-1 and MCP-1, followed by an almost equally rapid fall toward base-line levels by about 5 h postinjection. MCP-1 concentration in sera from the 11 subjects rose to a peak of 330 +/- 52 pM. The peak value for NAP-1 was 80 +/- 11 pM. In 10 of the 11 subjects, free IgG autoantibody to MCP-1 decreased from a mean pre-LPS value of 1820 +/- 660 pM to a mean low of 53% of the respective initial values. Corresponding data for IgG anti-NAP-1 were a pre-LPS concentration of 216 +/- 7 pM, which decreased to a mean low of 44% of the respective initial values. The finding in some subjects of a rapid rise in free antibody after the nadir suggests the possibility of acute regulation of autoantibody secretion rates. Although the results suggested that LPS-induced chemoattractant combined with free antibody, serum concentrations of MCP-1-IgG or NAP-1-IgG did not increase, which points to an as yet unknown mechanism for trapping and elimination of the immune complexes.

A human hepatoma (HepG2) cell line library was screened with an oligonucleotide probe for macrophage stimulating protein (MSP) to clone an MSP cDNA. Deduced sequences of isolated clones were compared with peptide fragment sequences of MSP. MSP9 cDNA encoded most of the known sequence of MSP except for a small segment of the 5' end of the open reading frame. Consequently, a hybrid 2300-base pair cDNA that encoded the complete MSP amino acid sequence was constructed from 2 clones. Culture fluid from COS-7 cells transfected with this full-length MSP cDNA had MSP biological activity, and the expressed MSP was detected by immunoprecipitation with antibody against native MSP. The deduced amino acid sequence of MSP includes 4 kringle domains, which have been found in hepatocyte growth factor and several proteins of the blood coagulation system. Among them, MSP has the highest sequence similarity to hepatocyte growth factor (45% identity). The MSP cDNA hybridized strongly to mRNA from liver, and to a lesser extent to mRNA from kidney and pancreas, suggesting that a cell type in the liver is the source of MSP. Several cloned and sequenced MSP cDNAs had insertions or deletions, suggesting that alternatively spliced MSP mRNAs may occur. This was reflected in Northern blots probed with an MSP cDNA, which showed more than one mRNA species. Furthermore, although the gene coding for MSP is on chromosome 3, the sequence of one of the cDNAs was identical with a unique sequence in chromosome 1, indicating that there may be a family of MSP genes, located on chromosomes 3 and 1.

Concentrations of MCP-1 and NAP-1 in culture fluids of human leukocytes were measured by sandwich ELISA. PPD caused PBMC's from tuberculin-sensitive subjects to secrete MCP-1 and NAP-1. PPD did not stimulate secretion by cells from a tuberculin-negative subject. Since the amounts secreted were more than could be produced by the few PPD-sensitized lymphocytes in the culture, we postulate that other cells were stimulated to secrete these chemoattractants. This study evaluated secretory capacity of one of the cell types in the PBMC culture. Unstimulated monocytes did not secrete MCP-1 or NAP-1. In order of increasing effect, IL-2 + IFN gamma, IL-1 alpha, and LPS caused monocyte secretion of MCP-1. The rank order for NAP-1 secretion was the same. TNF alpha did not cause secretion of MCP-1, but caused about the same amount of NAP-1 secretion as IL-2 + IFN gamma. Composition of the culture medium was especially critical for LPS-induced secretion of MCP-1, which was greatly enhanced by FCS and by Iscove's DMEM compared to RPMI 1640. IL-4 inhibited LPS-induced secretion of both MCP-1 and NAP-1. Secretory patterns were also a function of mononuclear phagocyte phenotype. LPS-induced secretion of MCP-1 was much greater for monocytes cultured several days in CSF-1 than for freshly isolated monocytes. LPS stimulation of bronchoalveolar macrophages caused NAP-1 secretion, but no secretion of MCP-1 above a relatively low baseline level.

Health care providers who combine to jointly negotiate contracts with third party payors risk violating the antitrust laws and incurring liability. This article describes the types of scrutiny to which joint activities are subject and outlines a number of factors that should be considered in analyzing the degree of antitrust risk involved in any joint provider arrangement.

In this communication, we have asked if MCP-1 is the mediator of cellular infiltration in DCH, outlining the criteria in Table 3. Preliminary data suggest that PHA-stimulated lymphocytes secrete MCP-1, and that MCP-1 can be produced in response to antigen stimulation. MCP-1 attracts monocytes and basophils, but not neutrophils. The question of a lymphocyte response to MCP-1 requires further study. We have emphasized that the discovery of leukocyte-specific NAP-1 and MCP-1 should now be followed by exploration of conditions in which one agonist is secreted without the other. This would be expected, for example, in DCH, which is characterized by mononuclear leukocyte infiltration without neutrophils.

A simple multiwell chamber is described that can be used to prepare randomly distributed cells on a microscope slide, suitable for morphological identification and differential counting. To the eight wells of the chamber are added 50-microliter volumes of cell suspension at concentrations of 10(3)-10(6) cells/ml. As the cells settle, fluid is slowly wicked away by a damp filter paper sandwiched between the microscope slide and the acrylic top plate of the multiwell chamber. Within 20-40 minutes, the cell monolayers on the slide are completely dry. The combined settling and bulk fluid removal results in a distribution of adherent cells that are sufficiently spread to exhibit excellent morphology after staining. If the chamber is centrifuged for 30 seconds at 50x g immediately after addition of cells, recovery of cells in the monolayer is virtually 100%, and as few as 50 input cells per 50 microliters can be detected. Agreement between predicted and observed differential counts of cell mixtures indicates that cells in the monolayer were distributed randomly.

The binding of human monocyte chemoattractant protein-1 (MCP-1) to human monocytes was studied. MCP-1 was radioiodinated with Iodo-beads (Pierce Chemical Co., Rockford, IL) without significant loss of biologic activity. 125I-MCP-1 binding to PBMC occurred within 5 min at 0 degrees C and the binding was inhibited by unlabeled MCP-1 dose dependently but not by neutrophil attractant/activation protein-1 or FMLP. 125I-MCP-1 bound to monocytes; no significant binding to either neutrophils or lymphocytes was observed. Scatchard plot analysis indicated that monocytes had a minimum of 1700 +/- 600 binding sites per cell with a Kd of 1.9 +/- 0.2 x 10(-9) M. For analysis of binding by flow cytometry, MCP-1 was biotinylated. In contrast to radioiodination, biotinylation resulted in loss of activity; potency was 10-fold less, but the efficacy was retained. Detection by flow cytometry of bound biotinylated MCP-1 with avidin-FITC confirmed results obtained with 125I-MCP-1. Biotinylated MCP-1 bound to monocytes but not to lymphocytes; and the binding was inhibited by a 100-fold excess of unlabeled MCP-1.

We have demonstrated inducible expression of the mRNA encoding the monocyte chemoattractant MCP-1, the human homolog of the JE gene, in endothelial cells within 3 hours of treatment with IL-1 beta and tumor necrosis factor. IFN-gamma also induced expression of this mRNA after 24 hours, but to a lesser extent. MCP-1/JE protein steadily accumulated in the medium of endothelial cells during a 48-hour exposure to IL-1 beta. Medium conditioned by IL-1 beta-treated endothelial cells contained monocyte chemoattractant activity that was immunoadsorbed by anti-MCP-1 antibodies. These results suggest that endothelial cells secrete a monocyte chemoattractant, MCP-1/JE, in response to inflammatory mediators, and thus may contribute to the accumulation of monocytes at sites of inflammation.

We recently purified human monocyte chemoattractant protein-1 (MCP-1) from culture fluids of either human glioma cell lines or mitogen-stimulated human peripheral blood mononuclear leukocytes. It has now been shown that MCP-1 is the product of the gene JE, which was first recognized by its expression in fibroblasts stimulated with platelet-derived growth factor (PDGF). We therefore studied secretion of MCP-1 by three human fibroblast cell lines. Monocyte chemotactic activity was found in culture fluids of all three lines after growth to confluence in DMEM-10% FCS, and the amounts secreted per cell were comparable for the three lines. The MRC-5 line was chosen for further study. Monocyte chemotactic activity secretion by confluent MRC-5 cultures continued after a switch to serum-free medium and was not inhibited by anti-PDGF antibody, indicating that secretion may not have been caused by autocrine release of PDGF. When concentrated serum-free MRC-5 culture fluid was injected into an HPLC gel filtration column, only one chemotactic activity peak was observed, which was in the same location as glioma-derived MCP-1. The activity was completely absorbed out by an anti-MCP-1 affinity column, which indicates that all the chemotactic activity in MRC-5 culture fluid was accounted for by MCP-1. PDGF caused a marked increase in chemotactic activity over that found in serum-free culture fluid of MRC-5 or 501T cells. Immunoprecipitation by anti-human MCP-1 showed two bands, corresponding to the two forms of MCP-1 previously described (MCP-1 alpha and beta); and the amounts increased in response to PDGF stimulation. Thus, the reported increase in human fibroblast JE mRNA in response to PDGF-containing serum stimulation is reflected in increased secretion of the MCP-1 gene product.

Neutrophil attractant/activation protein-1 (NAP-1) was previously shown to attract human neutrophils, but not monocytes. The purpose of this study was to determine if NAP-1 interacted with other types of blood leukocytes. In addition to its chemotactic activity for neutrophils, NAP-1 induced chemotactic responses by T lymphocytes and basophils. Chemotactic potency (10(-8) M for an optimal response) was the same for all three cell types. However, NAP-1 caused a chemotactic response in excess of random migration of 7% or 16% of basophils (depending on the medium used) and only 9% of T lymphocytes, in contrast to 30% of neutrophils. This agonist was not chemotactic for partially purified normal human eosinophils. The symmetrical histogram obtained by flow cytometry of neutrophils equilibrated at 0 degree C with fluoresceinated NAP-1 indicates that all neutrophils bound the ligand. A dose-response curve plateau, and inhibition of binding of NAP-1-FITC by unlabeled ligand are evidence for saturable binding to receptors, estimated to be 7000 per cell. Our results suggest that, for induction of an acute inflammatory response, the quantitatively significant action of NAP-1 is on neutrophils.

The addition of PHA to C3H mouse spleen cells in tissue culture led to the production of lymphotoxin (LT). Cytotoxicity was assayed by addition of the culture fluids to syngeneic target cells labeled with tritiated thymidine; after an incubation period of 72 hr the amount of radioactivity released into the supernatant was measured. The LT activity in unfractionated culture fluids survived lyophilization, remained unchanged for many weeks at 4°C, and progressively decreased on heating at 56°C for periods from 1 to 9 hr. Based on the G-200 Sephadex distribution coefficients for several preparations, the m.w. of mouse lymphotoxin was about 41,000 daltons. Lymphotoxin from three different spleen cell production runs was recovered from isoelectric focusing columns in sharply focused peaks, the pH of which ranged from 4.4 to 4.8.

C3H/HeN resident peritoneal macrophages in suspension culture supported continuous replication of L. tropica amastigotes; the total number of intracellular parasites increased 8- to 10-fold over 96 hr in culture. Lymphokine treatment of macrophages markedly affected intracellular replication of the Leishmania. Cultures treated with lymphokines before exposure to L. tropica were more resistant to infection, and 35% fewer cells contained intracellular amastigotes compared to medium-treated controls. Lymphokine-pretreated cells that became infected also inhibited the replication of intracellular amastigotes. Macrophage cultures treated with lymphokines after infection exhibited potent microbicidal activity; 75 to 80% of macrophages were free of intracellular parasites by 72 hr. Fractionation of lymphokine supernatants by Sephadex G-100 demonstrated 3 areas of activity for the induction of macrophage intracellular killing (130,000, 45,000, less than or equal to 10,000 daltons); one of these activity peaks (45,000-m.w. lymphokine(s)) also induced increased resistance to infection with L. tropica.

Cellular immune responses against larval and adult schistosome antigens were studied in attenuated cercariae-vaccinated P and C57BL/6 mice to define differences correlating with the inability of P mice to develop vaccine-induced resistance to challenge Schistosoma mansoni infection. Vaccinated P mice failed to demonstrate delayed hypersensitivity upon skin-testing with soluble worm antigens, whereas mice of the highly resistant strain C57BL/6 developed a significant 24-hr response to worm antigens in vivo. Also, when schistosome antigens were injected i.p., vaccinated P mice failed to exhibit an activated macrophage response in vivo, whereas vaccinated C57BL/6 mice developed macrophages with significant larvicidal and tumoricidal activity at the site of specific antigen challenge. Immune sera from either vaccinated C57BL/6 or P mice were equally effective at opsonizing the schistosomula targets in the larvicidal assay. In vitro analyses of cellular defects revealed that although T lymphocytes from vaccinated P mice showed blastogenic responses to schistosome antigens that were similar in magnitude and kinetics to those of cells from the C57BL/6 animals, T cells from C57BL/6 mice produced higher levels of macrophage-activating lymphokines (LK), including gamma-interferon. Macrophages from control C57BL/6 mice were also more responsive to activation by LK than macrophages from P mice were, as assessed by stimulation of these cells to kill skin-stage schistosomula in vitro. These two aspects of cellular dysfunction in P mice had the combined effect of rendering P macrophages incapable of activation by LK from mice of their own strain, whereas macrophages from C57BL/6 mice were strongly activated by LK from vaccinated C57BL/6 mice in the same assays. Thus, a correlation exists between T lymphocyte/macrophage dysfunction and lack of resistance to challenge infection in vaccinated P mice, which suggests that delayed hypersensitivity response plays a major role in the immunity to S. mansoni infection that is induced by exposure to radiation-attenuated cercariae.

Cell-mediated immune responses contributing to macrophage activation were compared in mice that demonstrated partial resistance to challenge Schistosoma mansoni infection as a result of vaccination with radiation-attenuated cercariae or of ongoing low-grade primary infection. Vaccinated mice developed significant delayed hypersensitivity reactions to soluble schistosome antigens in vivo. Splenocytes from vaccinated animals responded to in vitro culture with various specific antigens (soluble adult worm extract, living or disrupted schistosomula) by proliferation and production of macrophage-activating lymphokines as did lymphocytes from S. mansoni-infected animals. Macrophage-activating factors produced by spleen cells from vaccinated mice upon specific antigen stimulation eluted as a single peak on Sephadex G-100 with a molecular weight of approximately 50,000 and contained gamma interferon activity. Moreover, peritoneal macrophages with larvicidal and tumoricidal activity were recovered from vaccinated mice after intraperitoneal challenge with soluble schistosome antigens, a procedure also observed to elicit activated macrophages in S. mansoni-infected animals. These observations demonstrate that vaccination with irradiated cercariae stimulates many of the same cellular responses observed after primary S. mansoni infection, and suggest that lymphokine-activated macrophages may participate in the effector mechanism of vaccine-induced and concomitant immunity to challenge schistosome infection. This is the first demonstration of a potential immune effector mechanism in the irradiated vaccine model.

LPS stimulated human blood mononuclear leukocytes to produce a chemotactic factor for human neutrophils. The effect of LPS was dose-dependent; 10 micrograms/ml was optimal for production of chemotactic factor. Chemotactic activity was detected 3 hr after LPS stimulation, and reached its peak at 12 hr. No activity was detected in culture supernatants of unstimulated cells, provided LPS-free media were selected. Isoelectric point of the factor, determined by chromatofocusing, was approximately 8 to 8.5. Molecular weight was approximately 10 kilodaltons by Sephacryl S-200 gel filtration or by HPLC gel filtration on TSK-2000 and -3000 columns in succession. The gel filtration fractions were also assayed for IL 1 activity. The elution position of IL 1 activity corresponded to a m.w. of 18. There was no chemotactic activity in the IL 1 activity peak. Furthermore, highly purified natural Il 1 alpha and -beta and recombinant Il 1 alpha and -beta did not exhibit chemotactic activity for neutrophils in our assay. Among mononuclear leukocytes, the monocyte was the principal producer of neutrophil chemotactic factor. These results suggest that a chemotactic factor for neutrophils, different from IL 1, is produced by LPS-stimulated blood monocytes.

The appearance of lymphotoxin in the culture fluid of phytohemagglutinin (PHA)-stimulated mouse spleen cells required two cell fractions that were separated by adherence to plastic. Upon stimulation with PHA, neither cell fraction alone produced significant amounts of lymphotoxin; however, when the cell fractions were combined and then stimulated with PHA, full activity was produced. Cytotoxic activity was not fully restored by combining PHA-stimulated cultured fluids from adherent and nonadherent cell fractions. This indicated that the cytotoxic activity was not the result of two factors, one produced by each cell fraction, that acted on the target cells, but rather, two cells interacted to produce lymphotoxin. Treatment of the unfractionated spleen cells with monoclonal anti-Thy1.2 and complement before PHA stimulation greatly reduced the production of lymphotoxin and indicated that at least one of the cells was a T cell. Lymphotoxin production was partially restored by the addition of nonadherent cells to the anti-Thy1.2-treated cells, suggesting that the T cell was nonadherent. Treatment of unfractionated cells with either silica or carrageenan had no effect on the subsequent production of lymphotoxin by PHA, suggesting that the adherent cell was not actively phagocytic.

Lymphokine-rich culture supernatants of antigen- or mitogen-stimulated spleen cells were fractionated by Sephadex G-200 column chromatography; fractions were assayed for capacity to induce tumoricidal and rickettsiacidal activities in mouse macrophages. Lymphokine activity that activated macrophages for tumor cytotoxicity eluted as a single peak in the 45,000 m.w. region. In contrast, activity for intracellular killing of rickettsiae eluted in 3 distinct regions: 115 to 125,000, 35 to 45,000, and less than 10,000 daltons. This elution pattern was observed with both antigen and mitogen-induced lymphokines. Activity of each of the 3 lymphokine species for induction of rickettsiacidal activity was destroyed by heating at 56 degrees C for 1 hr. Tumor cytotoxicity and rickettsiacidal activity, both effector functions of activated macrophages, were dissociated on the basis of lymphokines regulating these activities.

Histamine in concentrations as low as 10(-8) M inhibited the chemotactic response of normal human basophils to C5a. Histamine had no effect on basophil chemotaxis to lymphocyte-derived chemotactic factor. Histamine inhibition of basophil chemotaxis to C5a was prevented by metiamide, a drug which blocks H2 receptors for histamine. Since the accumulation of basophils in delayed cutaneous basophilic hypersensitivity (CBH) reactions may occur in part because of chemotaxis to C5a, and since C5a can induce histamine release, histamine inhibition of chemotaxis may limit basophil infiltration in CBH lesions.

C3H/HeN resident peritoneal macrophages in suspension culture supported continuous replication of L. tropica amastigotes; the total number of intracellular parasites increased 8- to 10-fold over 96 hr in culture. Lymphokine treatment of macrophages markedly affected intracellular replication of the Leishmania. Cultures treated with lymphokines before exposure to L. tropica were more resistant to infection, and 35% fewer cells contained intracellular amastigotes compared to medium-treated controls. Lymphokine-pretreated cells that became infected also inhibited the replication of intracellular amastigotes. Macrophage cultures treated with lymphokines after infection exhibited potent microbicidal activity; 75 to 80% of macrophages were free of intracellular parasites by 72 hr. Fractionation of lymphokine supernatants by Sephadex G-100 demonstrated 3 areas of activity for the induction of macrophage intracellular killing (130,000, 45,000, less than or equal to 10,000 daltons); one of these activity peaks (45,000-m.w. lymphokine(s)) also induced increased resistance to infection with L. tropica.

Human blood monocytes comprise two subpopulations: one migrates to the chemoattractant, N-formylmethionyl-leucyl-phenylalanine (fMet-Leu-Phe), and has saturable binding sites for this peptide; the other does not migrate and exhibits little peptide binding. To determine if expression of binding sites was a function of monocyte maturation, we depleted human subjects of blood monocytes by leukapheresis so that the circulation was repopulated by monocytes released from the bone marrow. Pre- and postleukapheresis monocytes were then compared for fMet-Leu-[3H]Phe binding, superoxide generation, and chemotactic responses. No significant differences in peptide binding curves were found, suggesting that receptor expression was stable over the maturational span represented by these two groups of cells. This supports the hypothesis that there are two distinct lineages of monocytes with respect to expression of receptors for fMet-Leu-Phe. An additional finding of interest was that the number of chemotactically responsive cells immediately postleukapheresis was half the control. This was a transient state; monocyte responses were normal 3 hr after termination of leukapheresis, suggesting that they rapidly become functionally mature.

Culture fluids from five murine sarcomas were chemotactic for syngeneic peritoneal macrophages in vitro. Peritoneal macrophages from mice infected with Mycobacterium bovis, strain Bacillus Calmette-Guérin, were more responsive to the chemotactic factor in tumor cultures than were normal macrophages. Peritoneal granulocytes, however, did not significantly respond to this factor. The level of chemotactic activity in tumor cultures paralleled cell growth for all five tumors; maximal levels occurred during log growth. Culture medium alone or fluids from proliferating spleen cell cultures stimulated with mitogens did not have detectable chemotactic activity. Chromatography of the tumor culture fluids resulted in a single peak of chemotactic activity in the 15,000-molecular weight range on Sephadex G-100 and at about 7.5 mmho/cm specific conductance on diethylaminoethyl cellulose. By both biological and physicochemical characteristics, the chemotactic activity in tumor culture fluids was different from mouse lymphocyte-derived chemotactic factor.

Cellular immune responses against larval and adult schistosome antigens were studied in attenuated cercariae-vaccinated P and C57BL/6 mice to define differences correlating with the inability of P mice to develop vaccine-induced resistance to challenge Schistosoma mansoni infection. Vaccinated P mice failed to demonstrate delayed hypersensitivity upon skin-testing with soluble worm antigens, whereas mice of the highly resistant strain C57BL/6 developed a significant 24-hr response to worm antigens in vivo. Also, when schistosome antigens were injected i.p., vaccinated P mice failed to exhibit an activated macrophage response in vivo, whereas vaccinated C57BL/6 mice developed macrophages with significant larvicidal and tumoricidal activity at the site of specific antigen challenge. Immune sera from either vaccinated C57BL/6 or P mice were equally effective at opsonizing the schistosomula targets in the larvicidal assay. In vitro analyses of cellular defects revealed that although T lymphocytes from vaccinated P mice showed blastogenic responses to schistosome antigens that were similar in magnitude and kinetics to those of cells from the C57BL/6 animals, T cells from C57BL/6 mice produced higher levels of macrophage-activating lymphokines (LK), including gamma-interferon. Macrophages from control C57BL/6 mice were also more responsive to activation by LK than macrophages from P mice were, as assessed by stimulation of these cells to kill skin-stage schistosomula in vitro. These two aspects of cellular dysfunction in P mice had the combined effect of rendering P macrophages incapable of activation by LK from mice of their own strain, whereas macrophages from C57BL/6 mice were strongly activated by LK from vaccinated C57BL/6 mice in the same assays. Thus, a correlation exists between T lymphocyte/macrophage dysfunction and lack of resistance to challenge infection in vaccinated P mice, which suggests that delayed hypersensitivity response plays a major role in the immunity to S. mansoni infection that is induced by exposure to radiation-attenuated cercariae.