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The pathogenesis of lymphatic filariasis has been a matter of debate for many decades. Here, Gerusa Dreyer and colleagues propose a dynamic model of bancroftian filariasis, integrating clinical, parasitological, surgical, therapeutic, ultrasonographic and histopathological data. This model has profound implications for filariasis control programs and the management of the individual patient.

The value of the polymerase chain reaction (PCR) in the diagnosis of Wuchereria bancrofti infection was evaluated in comparison to microscopical examination of night blood smears, Nuclepore filtration, serology and ultrasonography. No correlation was found between PCR-based deoxyribonucleic acid (DNA) probing and serology. We did not find any evidence of free filarial DNA in either blood plasma or chylocoele fluid. We conclude that the 2 PCR-based techniques evaluated are not more sensitive than Nuclepore filtration for detection of W. bancrofti microfilaraemia, need at least 1 intact microfilaria in the volume of blood used for DNA extraction, and were much inferior to ultrasonography for detection of amicrofilaraemic adult worm carriers.

Prior studies indicate that a microfilarial stage-specific chitinase is a possible candidate antigen for a transmission-blocking vaccine against Brugian filariasis. The antigen is a functional enzyme that progressively appears as microfilariae mature and become able to infect and develop in a susceptible mosquito vector. It is recognized by a monoclonal antibody that reduces microfilaremia in infected animals and by a subset of sera from infected persons who remain amicrofilaremic. Immunization of jirds with recombinant chitinase induced partial protection against microfilaremia resulting from subsequent infection with Brugia malayi, but did not reduce adult worm burdens. Vaccination was much less effective when administered during the prepatent stage of infection and was ineffective when given to microfilaremic jirds. The protective epitope appears to be located close to the carboxy terminus of the chitinase molecule. Immunization of jirds with SXP1, an antigen present in multiple worm stages, also reduced microfilaremia and, in some experiments, adult worm burdens, but hyperimmunization with a recombinant filarial myosin was not protective. These observations indicate that the relative timing of immunization and infection is an important factor in the efficacy of antimicrofilarial vaccines.

We evaluated the usefulness of a recombinant parasite antigen (recSXP1) for the serologic diagnosis of lymphatic filariasis. A large proportion of sera from microfilaremic donors living in five different endemic countries (356 of 446 [80%]) contained IgG antibodies to recSXP1, as do sera from approximately 33% of amicrofilaremic patients with acute filarial disease and/or indirect evidence of active filarial infection. Exposure to filarial worms per se does not appear sufficient to elicit an anti-SXP1 antibody response. Thus, this serologic test identifies a large proportion of persons with active lymphatic filariasis among residents of endemic areas.

We evaluated the performance of Dot-enzyme-linked immunosorbent assays designed to detect species- and stage-specific antigens of Paragonimus westermani in sera with monoclonal antibodies as serodiagnostic tests for active paragonimiasis. Sera from all donors with parasitologically confirmed infections with P. westermani contained adult worm antigens, as did a high proportion of sera from persons suspected to be infected with this parasite. A smaller proportion of these sera also contained metacercarial stage-specific antigens. Sera from donors with other helminth infections, with confirmed pulmonary tuberculosis, or from healthy Chinese donors were nonreactive in the assay. Treatment of experimentally infected animals with praziquantel triggered a marked but transient increase in serum levels of adult P. westermani antigens, which then gradually disappeared within the next two months. The results of our studies indicate that the antigen-detection assay we have developed is a highly specific and sensitive diagnostic test for active infections with P. westermani.

We have isolated and characterized a gene encoding a novel GTP-binding protein of the GTPase superfamily in the filarial parasites Brugia malayi and Onchocerca volvulus. The deduced amino acid sequence of the cloned molecule has ∼ 30% overall homology to ras proteins and ∼ 90% homology to the ‘ras-like’ nuclear proteins TC4, ran and Spi1. Rabbit antisera to bacterially expressed filarial protein detect a 24-22 kDa doublet in extracts of adult B. malayi and mature microfilariae, which is absent from immature microfilariae,. Increased expression of the native parasite protein occurs when worms are cultured in the presence of epidermal growth factor.

By differentially screening an adult Brugia malayi cDNA library with sera from microfilaremic and amicrofilaremic donors infected with Wuchereria bancrofti, we have identified a novel parasite antigen denoted SXP-1. Recombinant SXP-1 filarial antigen is preferentially recognized by sera from microfilaremic persons with bancroftian filariasis and from skin snip-positive patients with onchocerciasis. Antibodies to SXP-1 are restricted to the IgG4 subclass and gradually decline after treatment with diethylcarbamazine. These findings indicate that it may be possible to replace microscopic examination of night blood films with a serological test designed to detect antibodies to a mix of SXP-1 and other suitable antigens for the diagnosis of microfilaremia due to bancroftian filariasis.

To evaluate the merit of antigen detection assays as a tool to monitor the efficacy of chemotherapy for lymphatic filariasis, we serially measured antigen levels in sera from jirds infected with Brugia malayi and from humans with bancroftian filariasis. Antigenemia was detected in all animals with parasitologically proven infection and was present in jirds with prepatent or occult filariasis. Antigen levels correlated with worm burdens, and progressively declined in drug-cured animals. Treatment with diethylcar-bamazine (DEC) triggered a transient increase in serum levels of filarial antigens bearing the epitope recognized by the monoclonal antibody HC 11. All patients with bancroftian filariasis became amicrofilaremic within one week after DEC treatment. Antigenemia levels slowly declined over a period of several months in all but one treated individual. Forty-two months after treatment, progressively rising antigen levels are present in 10 patients. Six of these remain amicrofilaremic; in the other 4, elevated antigenemia levels preceded or were detected at the same time as recurrent parasitemia. Periodic monitoring of antigenemia levels after treatment of patients with lymphatic filariasis can be used to identify individuals who are likely to develop recurrent microfilaremia before the parasites become detectable in blood samples, thereby allowing timely retreatment.

Differential diagnosis of Mycobacterium tuberculosis, M. avium, and other mycobacteria remains a lengthy process. Recently, the use of DNA probes has been proposed as a new approach for a more specific and rapid diagnosis. Here, we report the cloning and sequencing of a genus-specific probe for Mycobacterium and a species-specific M. avium probe. The genus-specific probe hybridizes with DNA from nine ATCC type strains and 13 isolates of mycobacteria but not to non-mycobacterial DNA. In addition, the cloned fragment could also be amplified by polymerase chain reaction (PCR) in DNa of ten different mycobacterial type strains. The M. avium specific probe hybridizes strongly to sequences amplified in M. avium but not other mycobacterial or non-mycobacterial DNA. Amplification of the target sequence by PCR allowed the detection of 1 fg of all mycobacterial DNA tested for the genus-specific probe and 1 fg of M. avium DNA for the species-specific probe.

Filarial parasites are just beginning to be studied at the genetic level. The potential of recombinant DNA technology for identifying parasite genes that are important in the pathogenesis of filarial disease or for the survival of the parasite is enormous. Work in several laboratories has already identified genes which encode ribosomal RNAs, as well as highly repeated DNA sequences that can be used as diagnostic probes. In addition, new methods to separate chromosomes will allow the physical mapping of parasite genes without the requirement for classical genetic analysis, which would be difficult in filariids.

The nature and intensity of immune reactions to filarial antigens appear to be controlled by two broad mechanisms: immunoregulation and immune tolerance. Parasite molecules of high molecular weight activate suppressor T lymphocytes; suppressive parasite products are present in sera from microfilaraemic patients. Prenatal or perinatal exposure to soluble parasite antigens may influence a person's future ability to react to filarial antigens.

Studies using conventional angiography or non-invasive scintigraphy have revealed widespread abnormalities in the lymphatics of the legs of patients with bancroftian filariasis, regardless of whether clinical lymphoedema is present. To determine if the observed changes were specific for filarial infections, we imaged the lymphatics of both legs in native residents of an area in Brazil where filariasis is not endemic. Study participants were matched by age, socioeconomic status and physical activities to patients with filariasis in Recife, evaluated in parallel. Based on textbook criteria, only one of 15 study participants had a completely normal lymphoscintigram. Modest to severe pathology of the leg lymphatics was observed in the remaining 14 residents of the non-endemic area and in 49 of 50 patients with bancroftian filariasis. These results indicated that factors other than filarial worms are a common cause of subclinical pathology of the leg lymphatics in north-eastern Brazil, and that the latter is not specific for bancroftian filariasis.

In many parasitic infections, dominant T helper cell (Th) type-2 CD4+ T cell responses exacerbate the disease. We have previously demonstrated that lacto-N-fucopentaose-III (LNFPIII), a sugar found on soluble egg antigens (SEA) of Schistosoma mansoni, stimulates splenic B cells from parasite-infected mice to proliferate and produce IL-10, a cytokine that promotes the generation of Th2 immune responses. In the present study, we extend our observations on ligand-specific activation of IL-10 producing B cells to leishmaniasis and lymphatic filariasis. We report here that infection with Leishmania major increases the splenic B220+ B cell subset in BALB/c mice, but not BALB/c. xid (lacking B-1 cells and carrying defective B-2 cells). In addition, these B cells secrete large amounts of IL-10 in vitro in response to stimulation with soluble leishmanial extract (LSE), LNFPIII, or SO4-Lewis(x). We also observed that injection of LSE increased the level of peritoneal exudate (PeC) B-1 cells (CD5+B220+) in BALB/c mice, but not C57BL/6, as compared to buffer-injected controls. Further, LSE elicited PeC B cells secreted IL-10 in response to LSE as well as to the sugars tested. A similar differential secretion of IL-10 by splenic B cells from BALB/c and BALB/c.xid was seen after S. mansoni infection. Likewise, injection of soluble microfilarial extract (MFX) resulted in an increase in percentage of PeC B-1 cells in BALB/c mice, but not C57BL/6, and these cells secreted IL-10 in response to stimulation with MFX or phosphorylcholine (PC). Collectively, these results suggest a correlation between expansion of ligand-specific IL-10 producing B and B-1 cells with dominance of Th2-type T cells in mice with the susceptible phenotype for these diseases.

We examined the periodicity and intravascular distribution of Wuchereria bancrofti microfilariae (mf) and determined the effect of these parasite properties on the accuracy of blood filming and filtration methods for diagnosis of bancroftian filariasis in the endemic area of Recife, Brazil. Microfilariae in both venous and capillary blood exhibited a nocturnal periodicity pattern with a relatively high amplitude. Overall, capillary blood contained approximately 1.25 times the number of mf present at the same time in the same volume of venous blood. However, the ratio of mf present in capillary and venous blood varied over a 24-hour period, so that the fewest mf were present in the capillary bed of the skin at the time when biting activity of the local Culex vector is the lowest. Twenty or 60 microliters blood films did not reliably detect carriers with fewer than 100 or 60 mf/ml venous blood, respectively, and were thus inadequate for the identification of low density mf carriers. In contrast, all carriers with > 1 mf/20 or 60 microliters blood smear at night could be identified during daytime hours by filtration of 1 micromilligram venous blood.

The ability of diethylcarbamazine (DEC) to kill adult Wuchereria bancrofti worms was evaluated by examining lymphatic nodules formed after treatment with 4 different treatment schedules of 193 males living in the endemic area of Greater Recife, Brazil. Lymphatic nodules appeared in the spermatic cord or upper extremities in 43 of 138 microfilaraemic individuals, in 3 of 30 amicrofilaraemic patients with filarial disease manifestations, and in 1 of 25 asymptomatic amicrofilaraemic residents of the endemic area treated with DEC. Fourteen of these nodules were surgically removed 10-150 d after the start of treatment. Regardless of the DEC dosage and schedule used, all nodules contained damaged and degenerating adult worms. An exuberant granulomatous process with large numbers of eosinophils and progressive fibrosis gradually developed around the dead parasites. The mechanism(s) by which DEC killed adult W. bancrofti could not be determined.

To determine the extent of lymphatic disease in persons infected with Wuchereria bancrofti who were microfilaraemic, we examined the superficial lymphatics of the legs by scintigraphy. In 4 endemic control subjects and in 10 of 14 clinically asymptomatic microfilaraemic individuals, lymphoscintigraphy revealed one major channel of lymphatic drainage in each leg. However, while trunk lymphatics were bilaterally symmetrical in the control, marked differences in the calibre of lymphatic vessels were observed in the microfilaraemic persons. Non-discrete lymphatics and a diffuse symmetrical distribution of collateral vessels in both legs were observed in all of 5 amicrofilaraemic patients with grade 2 lymphoedema. A similar diffuse drainage pattern was also seen in 3 previously microfilaraemic persons who had remained amicrofilaraemic and asymptomatic following treatment with diethylcarbamazine citrate (DEC). Thus, clearance of microfilaraemia by DEC therapy did not appear to reverse the type of lymphatic pathology observed in microfilaraemic subjects. The lymphoscintigraphy patterns did not correlate with serum levels of antibodies to 3 recombinant filarial antigens. Virtually all the asymptomatic microfilaraemic individuals infected with W. bancrofti examined had subclinical lymphatic disease detected by the non-invasive imaging technique of lymphoscintigraphy.

We examined the immunogenicity of various connective tissue proteins in patients with chronic onchocercal dermatitis and the effect of filarial proteases on this host-parasite interaction. Sera from patients with onchocerciasis reacted strongly with cuticular collagens from filarial parasites and with mammalian laminin. Some sera also contained antibodies to elastin and collagen type IV, but none reacted with collagen types I-III or fibronectin. This pattern of reactivity was characteristic for onchocerciasis: sera from patients with mansonellosis reacted strongly with collagen type IV but only weakly with laminin. Reactivity with mammalian laminin or collagen could not be absorbed with cuticular proteins from filarial worms and vice versa. Digestion fragments of laminin treated with filarial proteases retain antigenic determinants recognized by sera from patients with onchocerciasis. In contrast, proteases from Onchocerca volvulus adults and microfilariae drastically decreased the reactivity of the same sera with collagen type IV. These results indicate that filarial proteases may contribute to the pathogenesis of chronic onchocercal dermatitis, directly, by enzymatically destroying connective tissue of the skin, and indirectly, by triggering autoimmune responses to self-determinants on connective tissue proteins that are normally hidden within the supramolecular structure of the extracellular matrix complex.

Two Brugia malayi cDNA clones, denoted Bm 9 and Bm 21, were identified on the basis of immunoreactivity with human sera from microfilaremic and amicrofilaremic subjects infected with Wuchereria bancrofti, and the nucleotide sequence determined as described previously [1]. The complete nucleotide sequence and the deduced amino acid sequence of the larger clone (Bm 9) are shown in Fig. 1. Clone Bm 9 consists of 4049 bp and has a single, 3948-bp open reading frame (ORF) coding for a putative parasite protein of 1313 amino acids excluding the first three amino acids as derived from the synthetic linker. The ORF begins at nucleotide position 2. The invert of the nucleotide sequence of clone Bm 21 (2906 bp) is identical to the 3' region of clone Bm 9 (positions 961-3867) and, therefore, the ORF in clone Bm 21 is in the opposite direction to that of 2gtl 1 lacZ. A search of the PC/Gene R database (Release 6.60, IntelliGenetics Inc., CA 94040) revealed that Bm 9 is homologous to myosin. The highest level of homology is with the Caenorhabditis elegans myosin heavy chain B (MYSB$CAEEL, #P02566) [2] and with mammalian myosin sequences, especially the

Brugia malayi is a parasitic nematode that causes lymphatic filariasis in humans. The monoclonal antibody MF1, which mediates clearance of peripheral microfilaremia in a gerbil infection model, recognizes two stage-specific proteins, p70 and p75, in B. malayi microfilariae. cDNA coding for the MF1 antigen was sequenced, and the predicted protein sequence shows significant similarities to chitinases from bacteria and yeast. When microfilarial extracts and purified preparations of the MF1 antigen were tested for chitinase activity, strong bands of chitin-degrading activity comigrated in SDS/PAGE with p70 and p75 and showed a reduction-dependent mobility shift characteristic of the MF1 antigen. Thus, the MF1 antigen is microfilarial chitinase, which may function to degrade chitin-containing structures in the microfilaria or in its mosquito vector during parasite development and transmission.

Infectivity rates of insect vectors are the best criteria by which to assess the transmission of filarial parasites and the efficacy of filariasis control programs. Currently available DNA probes can be used to estimate the proportion of vectors containing larvae of a given filarial species but provide no information on three other important variables in the transmission dynamics of filarial nematodes: the developmental stage, the location and the actual number of larvae that are present in the vector, all of which can be reliably determined by microscopy. However, species identification is often difficult and sometimes impossible by conventional microscopy, which requires morphologically intact specimens. DNA is tough and DNA probing can identify worms that are dead and that have lost morphologic integrity; it also permits multiple analyses of the same specimen with different probes and has the potential for simultaneous processing of very large numbers of samples. Here, Senaroth Dissonoyake and Willy Piessens outline the route to the development of species- and life cycle stage-specific DNA/RNA probing reagents, and simple, reliable and quantitative technologies that can supplement and ultimately replace microscopic dissection.

A method for specific identification of mycobacteria by using the polymerase chain reaction on organisms taken from liquid cultures, frozen suspensions, or colonies grown on Lowenstein-Jensen slants is presented. This direct detection of mycobacterial organisms has important implications for strain typing and diagnosis.

A technique to identify Wuchereria bancrofti larvae in mosquito vectors with an enzyme-labeled DNA probe is described. To overcome the low sensitivity of nonradioactive detection methods, analyte DNA was amplified by polymerase chain reaction (PCR). Oligonucleotide primers were used to amplify W. bancrofti -specific DNA fragments of 380 and 650 bp, respectively. Parasite DNA in mosquito extracts was isolated free of inhibitors of the PCR by hybridization to a biotinylated DNA fragment (IWb 67), which hybridizes to DNA from most filarial species, followed by absorption of the resulting DNA hybrids onto avidin-coated acrylic beads. PCR-amplified DNA was detected with a biotin-labeled W. bancrofti -specific repeat DNA (IWb 35) coupled to avidin-alkaline phosphatase and the chemiluminescent substrate, AMPPD™. The DNA equivalent of less than one larva can be detected by this method in mosquito extracts. The sensitivity of detection was comparable to that of radioactive probes and the assay is suitable for field application in endemic countries.

We compared the chemical and immunological properties of cuticular collagens from four species of filarial nematodes, Onchocerca volvulus, O. gutturosa, Brugia malayi, and Dirofilaria immitis. The electrophoretic mobility of the major polypeptides extracted from adult worms is characteristic for each species studied. Cuticular collagens from adult worms and infective larvae differ in their susceptibility to proteases that cleave vertebrate collagens and to collagenases prepared from different developmental stages of filarial parasites. The overall amino acid composition of filarial collagens resembles that of vertebrate interstitial collagens and differs from that reported for collagens from free-living or intestinal nematodes. However, cuticular proteins of the four filarial species studied significantly differed in amino acid composition and in their reactivity with antisera to interstitial and basement membrane collagens of vertebrates.

In order to develop a serodiagnostic assay to detect antigens of Paragonimus westermani in biological specimens, we generated monoclonal antibodies to antigens of metacercariae and adult worms, and partially characterized the epitopes recognized by representative Mabs. Metacercarial stage-specific determinants were periodate-sensitive and protease-resistant, indicating that they are carbohydrate epitopes. In contrast, adult worm-specific determinants resisted periodate treatment but were sensitive to proteases, indicating that they are polypeptides. The majority of cross-reactive Mabs studied were directed against phosphorylcholine determinants. When used in a dot-ELISA, Paragonimus-specific Mabs could detect 0.3–7 ng/ml parasite antigen in human sera.

Studies in animal models indicate that antibodies to surface antigens of microfilariae participate in the control of parasitaemia resulting from infections with lymphatic filarial nematodes. In an attempt to identify parasite antigens that elicit such 'protective' host responses, we compared the antigen recognition patterns of persons who remained amicrofilaraemic after 3-6 years of exposure to Brugia malayi with those of individuals who developed patent filariasis during the same period. IgG antibodies in sera from immigrants identified between 0 and 25 microfilarial antigens on Western blots. The highest degree of reactivity was observed with antigens in the 65-75 kD and 20-30 kD ranges, and with a group of high mol. wt antigens (greater than 180 kD). Sera from amicrofilaraemic donors preferentially reacted with 70/75 kD microfilarial antigens. A proportion of such sera inhibited the binding of monoclonal antibody MF1 to its target epitope; eight of nine inhibitory sera were from patients with active infections, evidenced by the presence of microfilariae or filarial antigens in the donors' blood, but who were amicrofilaraemic. These results indicate that some amicrofilaraemic residents of areas where brugian filariasis is endemic develop immune reactions to a microfilarial stage-specific antigen that was previously identified as a potentially 'protective' parasite antigen in animal models of lymphatic filariasis.

Transplantable tumor lines were developed from 7,12-dimethylbenz[a]anthracene-induced mammary tumors in inbred WF rats. Although the primary tumors regressed following oophorectomy, the growth of late generations of the transplantable lines was not affected by castration or by treatment with estrogens, androgens, and progesterone. This result coincided with a change in the morphology of the tumors from well-differentiated to poorly differentiated anaplastic tumors. The transplantable mammary tumors were antigenic in vitro as evidenced by stimulation of syngeneic lymphocytes in mixed lymphocyte-tumor cell cultures. However, prior sensitization by excision of a first tumor graft failed to protect the animals against a second challenge with cells from the same tumor line.

The binding of Line 10 hepatoma cells to normal syngeneic guinea pig macrophages is increased when the tumor cells are treated with neuraminidase and galactose oxidase (NAGO) before they are added to the macrophage monolayers. The effect is abolished by exposure of the NAGO-treated tumor cells to sodium borohydride. Line 1 hepatoma cells treated with NAGO or with sodium periodate are killed to a greater extent than untreated tumor cells. This effect can also be reversed by sodium borohydride. Further, periodate-treated macrophages become cytotoxic for unmodified tumor cells. These results demonstrate that increased tumor cell killing occurs when artificial contacts (presumably via Schiff bases) are established between normal macrophages and tumor cells. They are consistent with the hypothesis that close cell to cell contact is necessary for macrophage-mediated cytotoxicity.

Guinea pig macrophages pretreated with the esterase inhibitor, antithrombin III (AT III) show increased responsiveness to macrophage-activating factor (MAF) as demonstrated by their enhanced cytotoxicity for tumor cells. Other proteins that are not esterase inhibitors did not enhance the effect of MAF on the macrophage. Enhancement of MAF activity was also obtained when macrophages were preincubated with the cell surface reactant, diazotized sulfanilic acid (DSA). These studies indicate that the effect of MAF can be enhanced by chemical modifications of the macrophage membrane. They also provide further evidence to support the hypothesis that an esterase on the macrophage membrane modulates this cell's responsiveness to lymphocyte mediators.

We investigated the mechanisms of specific immune unresponsiveness to microfilarial antigens. The blood of patients with obvious Brugia malayi infections contains an adherent cell type that specifically suppresses reactions to microfilarial antigens but not to other antigens. In the absence of continued stimulation by parasite antigens, this suppressor cell loses its functional activity after overnight culture in vitro. Furthermore, serums from patients with and without microfilaremia contain factors that also suppress reactions to filarial antigens in vitro. These results suggest that immune unresponsiveness in human beings with patent filarial infections is due to active suppression of immune responses directed against the parasite and not to an intrinsic inability of infected patients to react to parasite antigens. (N Engl J Med. 1980; 302: 833–7.)

The line-1 guinea pig hepatoma was used to study in vitro tumor cytotoxicity. Cytotoxicity was determined by measurement of the loss of tritiated thymidine-labeled target cells from culture vessels. With this technique, we demonstrated that significant tumor cytotoxicity was caused by lymphoid cells from tumor-immune guinea pigs, by cells from guinea pigs immunized against an antigen urelated to the tumor target, and by cell-free supernatants rich in lymphocyte mediators. Addition of normal peritoneal exudate cells enhanced the cytotoxic potential of a small number of highly purified immune lymphocytes, which suggested that recruitment of normal cells is an additional mechanism of tumor cell death in this system.

Normal guinea pig macrophages incubated for 3 days in vitro with mediator-rich lymphocyte supernatants become cytotoxic for the syngeneic tumors, Line 1 hepatoma and MCA-25 fibrosarcoma. Under identical experimental conditions the survival of two normal syngeneic cell types, fibroblasts and kidney cells, was not affected. The activating supernatants were prepared by stimulating sensitized lymphocyte cultures with an antigen unrelated to the target cells. Therefore, this type of macrophage-mediated cytotoxicity appears to be nonspecific but restricted to cells with malignant growth capacities.

The effect of BCG on the growth of transplantable rat mammary tumors in W/Fu rats was studied. Admixture of mycobacteria to tumor cells in vitro prior to their injection in vivo either had no effect on or resulted in inhibition of or enhancement of the growth of the tumor transplants. Inhibition occurred at high and enhancement at low mycobacteria:tumor cell ratios. However, following suppression of local tumor growth with high doses of BCG, the growth of a second tumor graft was enhanced. Pretreatment of rats with BCG alone also enhanced the growth of a subsequent tumor graft. These results suggest an inverse relationship between the optimal dose of BCG for suppression of local tumor and that required to induced systemic immunity.

Brugia malayi microfilariae of specified ages were obtained from gerbils implanted with fertile adult worms. Such microfilariae were tested for their capacity to infect mosquitoes. A strong age dependence was found for the microfilariae's capacity to: penetrate the mosquito midgut, exsheath in response to 20 mM calcium, and develop to third stage larvae in the mosquito. In addition, differences were found between 2-day-old microfilariae and controls (from larva-infected gerbils) in their reactivities with a series of monoclonal antibodies. Thus, defined immunochemical changes occur in microfilariae as they assume functional maturity.

To study the pathogenesis of tropical splenomegaly syndrome, we compared immunologic findings in patients from Flores, Indonesia, with those obtained in local residents without splenomegaly and in controls. Villagers with tropical splenomegaly syndrome had markedly elevated levels of total IgM, higher titers of IgM antibodies to Plasmodium vivax, and reduced levels of circulating T lymphocytes. The latter were caused by a decrease in the total number of T cells with the suppressor/cytotoxic phenotype (T8+). Levels of B lymphocytes were similar in all groups. All immunologic abnormalities reverted toward normal in patients treated weekly for 9 to 26 months with chloroquine phosphate. These findings suggest that overproduction of immunoglobulins in patients with tropical splenomegaly syndrome is caused by an imbalance in the normal ratio of helper: suppressor T cells that regulate B-lymphocyte function, and that this imbalance is due to a decrease in suppressor T lymphocytes. (N Engl J Med 1984; 31...

Normal peritoneal exudate cells (PEC) were activated as suspension cultures either in mediator-rich supernatants from o-chlorobenzoyl-bovine γ-globulin (OCB-BGG) stimulated lymphocytes or in antigen-free Sephadex fractions from these supernatants. After 24 hr incubation the activated macrophages showed enhanced cytotoxicity for line 1 hepatoma and were inhibited in migration. The adherent cell fractions of PEC, recovered by trypsinization from monolayers and activated by this technique, were as cytotoxic as unfractionated PEC. Lymphocyte supernatants and antigen-free fractions of the supernatants induced comparable macrophage-mediated tumor cytotoxicity. Treatment of activated macrophages with trypsin did not alter their cytotoxic capacity.

During recent years the immunological aspects of acute leukemia in man have been the subject of an ever increasing number of studies. Our purpose is to review progress made in four specific areas of research: the relationship between immune competence and susceptibility to leukemia, the role of immune competence during overt leukemia and its modification by chemotherapy, the characterization of leukemia antigens, and the effect of active immunotherapy on acute leukemia in man.

The effect of cytochalasin A and B, colchicine and vinblastine on tumor cell killing by macrophages activated in vitro with lymphocyte mediators was examined. Both cytochalasins reversibly inhibited the killing of tumor cells by activated macrophages. Kinetic studies with cytochalasin B suggested that this drug exerts its effect on an early step of the cytotoxic process. Additional studies revealed that the drug inhibited the binding of tumor cells by activated macrophages. Colchicine inhibited both the binding and the killing of tumor cells by activated macrophages, whereas its structural analogue, lumicolchicine, had no effect on either macrophage function. Vinblastine also inhibited the binding and killing of tumor cells. However, this drug no longer inhibited tumor cell binding at low concentrations ( −6 M ) that still inhibited tumor cell killing. Further, vinblastine inhibited tumor cell killing when added late to an ongoing cytolytic reaction. These results suggest that the cytochalasins, colchicine and vinblastine inhibit macrophage mediated cytotoxicity by preventing intimate contact between the effector macrophages and their targets. In addition, vinblastine also appears to inhibit a later step of the cytolytic process, possibly the secretion of a cytotoxic macrophage product.

Development in mosquitoes of Brugia malayi microfilariae obtained from the blood of jirds was compared to that of microfilariae from the peritoneal cavity. Penetration of the mosquito midgut wall as well as development into third-stage larvae was assessed. About 70% of blood-borne microfilariae penetrated the midgut wall whether ingested directly from a microfilaremic jird or from a membrane feeder containing blood from the same donor. In contrast, less than 30% of microfilariae from the peritoneal cavity penetrated the midgut wall. Microfilariae in the peritoneal cavity of jirds vary in ability to penetrate the midgut of mosquitoes; some penetrate as rapidly as do blood-borne microfilariae, others penetrate more slowly, and most fail to penetrate the midgut. Regardless of origin, microfilariae that penetrated the midgut wall developed into third-stage larvae.

Brugia malayi microfilariae and gravid adult females were examined to determine whether chitin (poly beta(1----4)-linked N-acetylglucosamine) is a structural component of the microfilarial sheath. Two lectins which are specific for beta(1----4)-linked oligomers of N-acetylglucosamine bind to the sheaths of living microfilariae. Diflubenzuron, a potent inhibitor of chitin synthesis in insects and crustaceans, causes gravid female worms to shed progeny microfilariae with truncated sheaths. A chitin-like fraction (hot alkali-insoluble and chitinase-sensitive) can be isolated from gravid female (but not male) worms. This fraction can be metabolically labelled with radioactive glucosamine, but such labelling is inhibited by diflubenzuron. These data suggest that chitin synthesis is critical to microfilarial sheath morphogenesis in this parasitic nematode.

We used a noncompetitive two-site ELISA with 5 monoclonal antibodies to determine whether parasite antigens are present in breast milk from women infected with Onchocerca volvulus. Seven out of 13 available milk samples contained significant amounts of filarial antigens. Antigen indices in milk correlated with levels of microfilarodermia (Rs = 0.74, P less than 0.005). Antigen-containing milk samples markedly inhibited mitogen-induced proliferation of human mononuclear cells and activated cells within this population that suppressed the proliferative response of autologous lymphocytes to mitogens and antigens. These findings indicate that parasite products are present in breast milk of O. volvulus-infected women and suggest that these may induce immune tolerance and/or suppression in infants born of infected mothers.

A case of Hodgkin's disease, associated with a reversible nephrotic syndrome that was believed to be due to compression of the inferior vena cava and renal veins by pathologic lymph nodes, is reported. Association of the 2 conditions, pathologic findings, and pathogenesis are briefly discussed. Emphasis is placed on the inclusion in work‐up of the nephrotic syndrome of inferior vena cava phlebography. Copyright © 1970 American Cancer Society

In a case of chronic thrombocytopenic purpura, significant lymphocyte transformation could be induced with autologous platelets as a stimulant. The reaction was not due to serum factors since it occurred when culture medium was supplemented either with autologous or pooled human serum. Controls excluded nonspecific lymphocyte transformation. Modulation of normal platelet antigens by viral or chemical factors or adsorption of such factors on the platelet membrane could account for the observed reactions. However, since other auto-antibodies were demonstrated, the hypothesis of altered cellular "self-recognition" mechanisms is tentatively proposed as an alternative explanation for this observation.

The effect of non-specific stimulation of the reticulo-endothelial system by Bacillus Calmette-Guerin (BCG) on growth of the DMBA-induced rat mammary tumor was studied after ovariectomy. BCG was administered at the nadir of tumor regression following ablation of the ovaries, either once as a single injection or at weekly intervals. Resumption of tumor growth, that occurred as expected in the untreated control group, was delayed at least three weeks after the single BCG injection and completely prevented when BCG was given weekly. These findings are discussed in relation to previous observations on the effect of BCG on mammary tumor growth in non-ovariectomized rats.