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Although asymptomatic haemophiliacs have been shown to have abnormalities of their immune response, independent of HIV, clinical evidence of significant immunosuppression is limited. The only clinical report has been an outbreak of M. tuberculosis in which a group of haemophilic boys appeared unduly susceptible to infection. These boys are now all HIV seropositive. Along with a group of HIV seronegative children with coagulation disorders and non-haemophilic HIV seropositive men, these boys have been restudied to examine immune response to PPD. The HIV seropositive haemophilic boys that had had M. tuberculosis infection had reduced cytolytic response to PPD pulsed macrophages comparable to the non-haemophilic HIV seropositive men. The HIV seronegative children with coagulation disorders showed a reduction in cytolytic activity at low effector:target ratios compared to normal controls. In vitro studies showed that exogenous factor VIII concentrate could inhibit cytolytic activity to PPD pulsed macrophages. The possible role of chronic blood-borne virus infection and factor VIII concentrates in the original outbreak are discussed.

Although neonatal vaccination with bacille Calmette-Guérin (BCG) is considered to be safe, complications with disseminated disease are associated with underlying immuno-deficiency disorders. A BCG-vaccinated 4-month-old girl of Sri Lankan parentage developed progressive left axillary lymphadenopathy and severe bronchopneumonia. Lymph node biopsy demonstrated epithelioid granulomata and acid-fast bacilli. An older sibling had had a similar clinical presentation and the outcome had been fatal. Investigation for immuno-deficiency detected complete IL12RB1 deficiency. Full recovery followed a prolonged course of anti-tuberculous chemotherapy. She was put on lifelong isoniazid prophylaxis. In HIV-negative infants with unusual complications related to BCG vaccination, a primary immuno-deficiency disorder should be considered.

Background: Common variable immune deficiency (CVID) is prone to under‐diagnosis and may not reach relevant specialists until late in life. Morbidity is most commonly due to acute‐on‐chronic respiratory infections leading to respiratory failure. Aim: To investigate respiratory complications, lung function and high‐resolution computerized tomography scan (HRCT) findings and mortality in 47 patients with CVID. Setting: A regional immunology unit (Birmingham Heartlands Hospital). Design: Retrospective observational case‐note study following the introduction of shared care between immunology and respiratory medicine. Results: Age at diagnosis ranged from 5 to 72 years, with a median time from development of first symptoms to diagnosis of 4.0 years. There was delay in referral between chest physicians and immunologists, (median referral time between specialities >5 years). Forty‐two patients had respiratory complications, due to bronchiectasis ( n =32), asthma ( n =7), recurrent chest infections ( n =9) without concomitant evidence of structural lung damage, and granulomatous lung disease ( n =2). Spirometry was abnormal in 10/39 patients (7 obstructive, 3 restrictive). Bronchiectasis was confirmed on chest radiograph ( n =9) and HRCT ( n =24). Despite the high prevalence of bronchiectasis, few patients had received instruction in physiotherapy and sputum culture results were sparse. Discussion: To reduce the morbidity associated with CVID, there needs to be greater awareness of respiratory complications, particularly amongst physicians caring for such patients. Emphasis has been placed on adequate dosage of immunoglobulin, but early involvement by a respiratory physician is essential to monitor lung function and initiate optimal therapy, to minimize the occurrence and progression of lung damage.

Investigation of the P2X 7 receptor-associated signalling events following ATP stimulation of Mycobacterium bovis BCG-infected human macrophages revealed that ATP-mediated cell death and associated mycobacterial killing could be functionally uncoupled. Inhibitors of phospholipase D (PLD) (wortmannin and butan-1-ol), phospholipase A 2 (PLA 2 ) (GW 624A and GW 625A) and the mitogen-activated protein kinase (MAPK) pathway (SB203580 and PD98059) all antagonised the ATP-mediated killing of intracellular mycobacteria, but had no effect on ATP-induced macrophage death. Inhibitors of protein kinase C (PKC), protein tyrosine kinases (PTKs), and protein serine/threonine phosphatases (PSTPs) were ineffective against either ATP-stimulated cell death or bacterial killing. The mycobactericidal effects of ATP were not associated with the induction of apoptosis per se as the broad spectrum caspase inhibitor, ZVAD-fmk, failed to block killing of mycobacteria within human macrophages. Inhibitors of protein synthesis (cycloheximide) and transcription (actinomycin D) were also ineffective against the cytotoxic and bactericidal responses of ATP, suggesting that the terminal effector mediator(s) involved is preformed and does not require de novo synthesis. Immunoelectron microscopy studies using intracellular probes to identify lysosomes revealed that ATP treatment of BCG-infected macrophages induced the progressive colocalisation of mycobacteria-containing phagosomes with lysosomes. The data suggests that ATP-induced killing of intracellular mycobacteria involves the cellular activation of PLD, PLA 2 , and MAP kinase, and these signalling events lead to the maturation of the BCG-containing phagosome culminating in the demise of the invading mycobacteria.

the first, aVected individuals, particularly siblings usually residing in regions geographically related to outBackground. In a recent study of three families we have found that inherited haemolytic uraemic syn- breaks of HUS, suVer disease within days or weeks of each other and temporally related to the outbreak. It drome (HUS ) maps to a region of chromosome 1q containing the gene for complement factor H. In one is likely that an infectious agent is responsible. The second familial form of HUS occurs at diVerent times of these families and also in a case of sporadic DHUS, we have identified mutations in the factor H implying an inherited predisposition. In this form prognosis is poor, mortality is high (often over 50%) gene. A further family with inherited HUS has therefore been investigated. and recurrence is not uncommon. In a recent study of three families, we have found that inherited HUS maps Methods. DNA extracted from the family members and DNA extracted from archival post-mortem mat- to a region of chromosome 1q containing the gene for complement factor H. In one of these families, and erial from a deceased family member, was studied. Review of renal biopsies and study of complement also in a case of sporadic D-HUS, we have identified mutations in the factor H gene [2]. components was also undertaken. Results. This family demonstrates an inherited defi- We now present a further family in which an inherited deficiency of complement factor H is associated ciency of complement factor H. Non-diarrhoeal HUS has aVected at least two family members with half with HUS. normal levels of factor H. Conclusion. These findings represent further evidence of the association between factor H dysfunction and Family pedigrees and case histories (Figure 1) HUS. II-4 (Index case)

Aims-To overcome the problems associated with proteolytic pretreatment of tissue sections for the detection of apoptosis.Methods-Formalin fixed, paraffin wax embedded tissue sections of reactive lymph nodes and biopsy specimens of Burkitt lymphoma were pretreated by pressure cooking for the detection of apoptosis using the in situ end-labelling and in situ nick translation methods.Results-The results achieved with the in situ end-labelling and nick translations methods were compared with those obtained using a novel anti-apoptosis specific protein (ASP) antibody. The staining patterns generated using the three methods were similar and consistent, although the ASP antibody seemed to be more sensitive and detected higher numbers of apoptotic cells within sections.Conclusions-Pressure cooking is advocated as an alternative method to proteolytic enzyme digestion for pretreating paraffin wax sections. It is reliable, inexpensive, reduces the need to optimise pretreatment variables for different tissues, and permits double immunostaining of sections.

AIMS--To evaluate two of the recent methods of coating microtitre plates in the enzyme linked immunosorbent assay (ELISA) for detecting human antibodies against meningococcal capsular polysaccharides A and C with a view to validating a specific meningococcal antibody assay for routine clinical use. METHODS--Two four-layer ELISA protocols were standardised: one method utilised meningococcal polysaccharides conjugated to poly-L-lysine polypeptide for coating the microtitre plates; another used polysaccharides mixed with methylated human serum albumin (mHSA). Titration curves were plotted for the ELISAs and the squared Pearson correlation coefficient (R2) was used to determine the degree of accuracy of fit of the curves. Specificity tests were performed by inhibition and adsorption studies. RESULTS--Both methods gave good titration curves with a high R2 of > 0.98, indicating a high degree of accuracy in forming the curves. The titration end point after vaccination, obtained by the mHSA method, was 20 times higher, however, than that obtained by the poly-L-lysine method. Specificity tests showed that in the ELISA using polysaccharide/poly-L-lysine, antibody activity of a pre-vaccination serum sample was inhibited by 37%, and of post-vaccination serum by 50% with 1000-fold excess antigen. Antibody activity (post-vaccination) was reduced by 51% and 59%, respectively, by adsorption with antigen-coated Sepharose beads or adsorption with suspensions of killed meningococci. In contrast, antibody activity of a pre-vaccination serum was inhibited by 60% and a post-vaccination serum by 90% in ELISA employing polysaccharides mixed with mHSA. Reproducibility was better with the use of methylated human serum albumin than with poly-L-lysine; the former showed intrabatch and interbatch coefficients of variation of 4% and 2%, respectively, compared with 43% (intrabatch) and 16% (interbatch) obtained with the poly-L-lysine. CONCLUSION--It is concluded that the antibody assay using meningococcal polysaccharides groups A and C mixed with mHSA is much better than that using polysaccharides coupled with poly-L-lysine.

Stimulation of human CD4+ T cell clones with appropriate specific peptides or with lectins in the absence of APC induces a substantial degree of cell death. We have investigated the mechanisms of induction of this cell death and show that it occurs by apoptosis, identified by morphology and the characteristic pattern of DNA degradation. We also investigated whether this T cell death was a result of a suicide process activated in the T cell after "inappropriate" recognition of Ag on the surface of another T cell clone (and in the absence of other accessory signals), or was due to a conventional lethal hit delivered by one cytolytic T cell to another "target" T cell. Our results strongly suggest that peptide-induced cell death of human CD4+ CTL is due to active killing of Ag-presenting target T cells by effector T cells of the same clone. The cell death that is induced in the target T cell occurs via apoptosis that requires de novo RNA transcription and translation in the effector T cell.

High-dose intravenous immunoglobulin (IVIG) therapy has been effective in many autoimmune and systemic inflammatory diseases including polymyositis (PM) and dermatomyositis (DM). In the present study we evaluated the efficacy of IVIG using experimental models of PM and DM. An experimental autoimmune myositis (EAM) model was produced in SJL/J mice by an immunization with rabbit myosin B (MB) fraction. In this model, the plasma level of anti-MB antibody was elevated, and mouse IgG and complement C3 were deposited in the muscle fibres. Administration of IVIG dose-dependently reduced the incidences of necrotic and inflammatory changes in the skeletal muscle. IVIG treatment also decreased the elevation of anti-MB antibody level, as well as the deposition of IgG and C3. We next evaluated the effect of IVIG in adoptive EAM mice made by an intravenous injection of lymph node cells previously stimulated with MB. Adoptive EAM mice showed similar lesions in skeletal muscle as EAM mice and IVIG inhibited the lesion development. In vitro experiments demonstrated that IVIG inhibited complement-mediated lysis of human erythrocytes sensitized with anti-human erythrocyte antibodies. The binding of C1q, C4 and C3 to the same cells was also inhibited by IVIG. Taken together these findings suggest that IVIG prevents the development of myositis in EAM and adoptive EAM models by several mechanisms, such as reducing anti-myosin antibody and by blocking complement activation. Our present findings might account for the clinical efficacy of IVIG in PM and DM patients.

The case of a previously healthy HIV seronegative woman with disseminated Mycobacterium tuberculosis infection and markedly reduced interferon gamma production is reported here. Complete healing of her disseminated lesions was seen only after addition of subcutaneous interferon gamma to her tuberculosis treatment.

International audience; The human peripheral B-cell compartment displays a large population of immunoglobulin M-positive, immunoglobulin D-positive CD27(+) (IgM(+)IgD(+)CD27(+)) "memory" B cells carrying a mutated immunoglobulin receptor. By means of phenotypic analysis, complementarity-determining region 3 (CDR3) spectratyping during a T-independent response, and gene-expression profiling of the different blood and splenic B-cell subsets, we show here that blood IgM(+)IgD(+)CD27(+) cells correspond to circulating splenic marginal zone B cells. Furthermore, analysis of this peripheral subset in healthy children younger than 2 years shows that these B cells develop and mutate their immunoglobulin receptor during ontogeny, prior to their differentiation into T-independent antigen-responsive cells. It is therefore proposed that these IgM(+)IgD(+)CD27(+) B cells provide the splenic marginal zone with a diversified and protective preimmune repertoire in charge of the responses against encapsulated bacteria.

A region 2 kb upstream of exon 1 of the P2X7 gene was sequenced using DNA from nine healthy individuals who exhibited three different ATP response phenotypes (i.e. high, low and interferon gamma-inducible). Five single nucleotide polymorphisms were identified within the nine donor promoter sequences but none were associated with a specific ATP response phenotype. A P2X7 loss of function polymorphism (1513 in exon 13) was also screened for within donor DNA but no response associations were identified. ATP response phenotype was positively associated with P2X(7) receptor expression, as assessed by flow cytometry, but not with any identified receptor or promoter gene polymorphisms.

Patients with genetic lesions in the Type-1 cytokine/cytokine receptor pathway exhibit a selective susceptibility to severe infections with poorly pathogenic mycobacteria and non-typhi salmonella spp. These experiments of nature demonstrate that IL-12-dependent IFNgamma production is critical for granuloma formation and therefore host immunity against such pathogens. The essential role of granuloma formation for protective immunity to these organisms is emphasized by the differing granuloma forming capabilities and resultant clinical sequelae observed in these patients which seems to reflect their ability to produce or respond to IFNgamma (Fig. 9). At one pole of this spectrum, represented by the complete IFNgammaR1/2 deficient patients, there is a complete absence of mature granuloma formation, whereas with the less severe mutations (i.e. partial IFNgammaR1/2, complete IL-12p40 and complete IL-12Rbeta1 deficiency), granuloma formation is very heterogenous with wide variations in composition being observed. This suggests that in the latter individuals, who produce partial but suboptimal IFNgamma responses, other influences, including pathogen virulence and host genotype may also affect the type and scale of the cellular response elicited.

Following infection with intracellular pathogens like mycobacteria, listeria, toxoplasma and leishmania, mononuclear phagocytes and related antigen-presenting cells (APC), i.e. dendritic cells, secrete the heterodimeric cytokine IL-12. IL-12 comprises two disulphide-linked subunits, p40 and p35, which together form the biologically active p70 hetrodimer molecule (reviewed in [1,2]). IL-12 production by macrophages and dendritic cells can also be enhanced by a T cell-dependent pathway through interaction of CD40 on the surface of the APC with CD40-ligand expressed on activated T cells. The IL-12 receptor (IL-12R), which is expressed by both natural killer (NK) cells at certain stages of development and by activated T cells, is made up of two chains called IL-12Rβ1 and IL-12Rβ2, respectively. Both receptor chains have extracellular, transmembrane and intracellular segments. Each of these receptor proteins can only bind to IL-12 with low affinity, but when co-expressed can bind IL-12 with high affinity, initiating a physiological response to this cytokine [3]. A schematic representation of the IL-12 receptor-mediated intracellular signalling pathway is illustrated in Fig. 1. Fig. 1 Binding of IL-12 to the IL-12Rβ1 and β2 chains induces phosphorylation of the kinases Tyk2 and Jak2, which associate with the cytoplasmic tails of the β1 and β2 chains, respectively. Subsequently the signal transducing ... Binding of IL-12 to activated CD4 T cells partitions them to develop and differentiate along the so-called Th1 pathway, crucially important for cell-mediated immunity against intracellular pathogens. Furthermore, acting at picomolar and subpicomolar levels on T cells and NK cells, IL-12 induces high-level production of the cytokine IFN-γ[2]. IFN-γ plays a central role in the resistance of mammalian hosts to pathogens, particularly bacteria and parasites capable of intramacrophage survival (reviewed in [4,5]). The main cells producing IFN-γ are activated Th1 cells, activated CD8 cytotoxic cells of the TC1 phenotype, and activated NK cells. Biologically active IFN-γ is a homodimer, which has a range of pleiotropic effects on a number of cell types, with the ability to modulate the function of over 200 genes. It is one of the principal macrophage-activating cytokines, and mice with disrupted IFN-γ or IFN-γ receptor (IFN-γR) genes show increased susceptibility to intracellular pathogens including Leishmania major, Listeria monocytogenes, mycobacteria and certain viruses, e.g. vaccinia virus. IFN-γ interacts with a specific cell surface receptor, which is widely expressed on most nucleated cells. The IFN-γR consists of two transmembrane proteins, namely IFN-γR1 which is a ligand-binding chain, and IFN-γR2, which is required for signal transduction. A schematic representation of the IFN-γ receptor-mediated intracellular signalling pathway is shown in Fig. 2. Fig. 2 A schematic representation of the IFN-γ receptor-mediated intracellular signalling pathways (modified from [4,5]). Two IFN-γR1 chains dimerize on binding the IFN-γ homodimer and subsequently associate with two IFN-γR2 chains. ... Key actions of IFN-γ include increased expression of MHC class I and class II proteins which enhance antigen processing and presentation, activation of mononuclear phagocytes through a multiplicity of effects, influencing IgG heavy-chain switching and modulating the production of cytokines such as IL-12, tumour necrosis factor-alpha (TNF-α) and IFN-γ itself. Following IFN-γR ligation the receptor–ligand complexes recycle into an acidified subcellular compartment, where they dissociate. Free IFN-γ is then degraded by lysosomal enzymes. The uncoupled IFN-γR1 receptors eventually relocate to the cell surface via an intracellular pool. An amino acid motif present on the intracellular domain of the IFN-γR1 close to the Jak1 association site is required for normal recycling of this receptor (Fig. 2). The above background information helps in the understanding of the clinical, pathological and immunological features of defects in the IL-12-dependent, high-output IFN-γ pathway and the laboratory methods required for identifying these defects.

Genetic lack of interleukin 12 receptor beta1 (IL-12Rbeta1) surface expression predisposes to severe infections by poorly pathogenic mycobacteria or Salmonella and causes strongly decreased, but not completely abrogated, interferon (IFN)-gamma production. To study IL-12Rbeta1-independent residual IFN-gamma production, we have generated mycobacterium-specific T cell clones (TCCs) from IL-12Rbeta1-deficient individuals. All TCCs displayed a T helper type 1 phenotype and the majority responded to IL-12 by increased IFN-gamma production and proliferative responses upon activation. This response to IL-12 could be further augmented by exogenous IL-18. IL-12Rbeta2 was found to be normally expressed in the absence of IL-12Rbeta1, and could be upregulated by IFN-alpha. Expression of IL-12Rbeta2 alone, however, was insufficient to induce signal transducer and activator of transcription (Stat)4 activation in response to IL-12, whereas IFN-alpha/IFN-alphaR ligation resulted in Stat4 activation in both control and IL-12Rbeta1-deficient cells. IL-12 failed to upregulate cell surface expression of IL-18R, integrin alpha6, and IL-12Rbeta2 on IL-12Rbeta1-deficient cells, whereas this was normal on control cells. IL-12-induced IFN-gamma production in IL-12Rbeta1-deficient T cells could be inhibited by the p38 mitogen-activated protein kinase (MAP) kinase inhibitor SB203580 and the MAP kinase kinase (MEK) 1/2 inhibitor U0126, suggesting involvement of MAP kinases in this alternative, Stat4-independent, IL-12 signaling pathway.Collectively, these results indicate that IL-12 acts as a partial agonist in the absence of IL-12Rbeta1. Moreover, the results reveal the presence of a novel IL-12Rbeta1/Stat4-independent pathway of IL-12 responsiveness in activated human T cells involving MAP kinases. This pathway is likely to play a role in the residual type 1 immunity in IL-12Rbeta1 deficiency.

Bio Products Laboratory (BPL), the main fractionator of plasma-derived medicines, are undergoing a change from UK plasma to plasma from the USA. BPL aim to maintain continuity of supply and a seamless changeover, despite meticulous cleaning of its production plant and months of auditing by both the organization and regulatory authorities.

The measurement of immunoglobulin A (IgA) endomysial antibodies is now established as an important diagnostic test in gluten-sensitive disease. Monkey oesophagus is the commonly used tissue substrate, but it has been proposed that human umbilical cord tissue may be a suitable alternative for antibody detection. In this study, we report a modified method of examining endomysial antibody reactivity with cord tissue. This involves examination of antibody reactivity with cells in Wharton's jelly, and with umbilical cord blood vessel. A total of 370 patients being investigated for coeliac disease were studied and this diagnosis was established in 42. Endomysial antibodies were found in all 42 using umbilical cord tissue, and the test results were confirmed with monkey oesophagus substrate. In three of the remaining 328 non-coeliacs, a false-positive endomysial antibody test was noted and small intestine histology was normal in these patients. All positive sera were found to react with cells in Wharton's jelly, and reticular staining of blood vessels was also present. Examination for immunofluorescence in both Wharton's jelly and blood vessel components of cord tissue greatly simplified test interpretation.

Interferon-gamma receptor ligand-binding chain (IFN-gammaR1) or signaling chain (IFN-gammaR2) deficiency, like interleukin 12 receptor beta1 chain (IL-12Rbeta1) deficiency, predispose to severe infections due to poorly virulent mycobacteria and salmonella. A child with bacille Calmette-Guerin and Salmonella enteritidis infection was investigated. Mutations in the genes for IFN-gammaR1, IFN-gammaR2, IL-12Rbeta1, and other molecules implicated in IL-12- or IFN-gamma-mediated immunity were sought. A large homozygous deletion within the IL-12 p40 subunit gene was found, precluding expression of functional IL-12 p70 cytokine by activated dendritic cells and phagocytes. As a result, IFN-gamma production by lymphocytes was markedly impaired. This is the first discovered human disease resulting from a cytokine gene defect. It suggests that IL-12 is essential to and appears specific for protective immunity to intracellular bacteria such as mycobacteria and salmonella.

The death of BCG-infected human macrophages induced in vitro by ligation of surface CD95 (Fas), CD69, or complement-mediated lysis was shown not to result in the death of intracellular mycobacteria, whereas exposure to extracellular ATP initiated both macrophage death and killed the intracellular bacteria. ATP acted via P2Z receptors because these effects were mimicked by benzoylbenzoic ATP (a known agonist of P2Z receptors) and blocked by oxidized ATP, DIDS, suramin, amiloride, and KN62 (known inhibitors of P2Z-mediated responses). ATP-mediated bacterial killing was independent of reactive nitrogen and oxygen intermediates and of actinomycin D or cycloheximide inhibition. ATP-induced macrophage cell death, BCG killing, and lucifer yellow dye incorporation were minimal in 2 out of 19 healthy donors. The results suggest possible genetic heterogeneity of this mechanism of mycobacterial killing associated with P2Z-mediated pore formation.

BACKGROUND: Macrophage activation by cytokines provides only a partial explanation of antimycobacterial immunity in man. Because cytolytic T lymphocytes have been shown to contribute to immunity in animal models of intracellular infection, the generation of mycobacterial antigen specific cytotoxic T cells was examined in the peripheral blood of patients with tuberculosis. METHODS: Subjects comprised 36 patients with active tuberculosis (18 newly diagnosed) and 32 healthy volunteers, of whom 25 had had BCG vaccination and seven were Mantoux negative. The ability of purified protein derivative (PPD) stimulated peripheral blood lymphocytes to lyse autologous, mycobacterial antigen bearing macrophages was examined by using a chromium 51 release assay. RESULTS: PPD stimulated lymphocytes from normal, Mantoux positive, BCG vaccinated subjects produced high levels of PPD specific cytolysis, whereas lymphocytes from unvaccinated, uninfected subjects caused little or no cytolysis. The generation of cytolytic T lymphocytes by patients with tuberculosis was related to their clinical state. Those with cavitating pulmonary disease or lymph node tuberculosis generated PPD specific lymphocytes with cytotoxic ability similar to that of those from Mantoux positive control subjects, whereas lymphocytes from patients with non-cavitating pulmonary infiltrates showed poor antigen specific cytolysis. After seven days of stimulation with PPD in vitro, lymphoblasts contained both CD4+ and CD8+ cells. Mycobacterial antigen specific cytolysis was restricted to the CD4+ cell population and was blocked by monoclonal antibodies directed against major histocompatibility class II (MHC) antigens. CONCLUSION: CD4+ cytolytic T cells can lyse autologous macrophages presenting mycobacterial antigen and were found in patients with cavitating pulmonary tuberculosis or tuberculous lymphadenitis and in normal, Mantoux positive control subjects. The ability to generate these T cell responses seems to be a marker for response to mycobacteria and may contribute to tissue damage in tuberculosis. These responses do not provide protective immunity against Mycobacterium tuberculosis but may help in disease localisation.

SUMMARY Culture studies have suggested that Mycobacterium paratuherculosis may play a role in the aetiology of Crohn's disease. However, evidence of sensilizalion to mycobactcrial antigens amongst patients with Crohn's disease has not yet been adequately demonstrated. Previous studies of cell-mediated immunity (CMI) in Crohn's disease were restricted to responses of peripheral blood mononuclcar cells (PBMC) to mycobacterial antigens. In this study we have investigated the proliferativc responses of both PBMC and mesenteric lymph node mononuclcar cells (MLNMC) to a range of mycobacterial and non-mycobactcrial antigens. There was no evidence of specific sensitization in the responses of MLNMC and PBMC from patients with inflammatory bowel disease (IBD) to the mycobacterial antigens. However, anergy to M. paratuherculosis could not be excluded. IBD MLNMC responses to most antigens were generally greater than those of PBMC. which were often undetectable. When compared with controls, there was evidence of increased CM 1 to a range of non-mycobactcrial antigens, especially Yersinia enterocolitica. amongst both MLNMC and PBMC from patients with Crohn's disease and ulcerative colitis (UC). These results do not provide support to the proposed role of mycobacteria in the pathogcnesis of Crohn's disease, but indicate that further investigation may determine a role for bacterial-specific T cell-mediated responses in the palhogcncsis of IBD.

Mycobacterium tuberculosis is an obligatory parasite with no free-living (saprophytic) forms. It has the capacity to survive and multiply within mononuclear phagocytes (i.e. monocytes and macrophages), as well as survive extracellularly. Unlike pyogenic bacterial pathogens, mycobacteria multiply slowly with a generation time of 12–24h. In consequence, tuberculosis is a chronic disease which is slow to develop and progress (cf. meningococcal septicaemia). The tubercle bacillus is well adapted to be a successful parasite in the human host and can survive for many years within an infected host. Factors which contribute to the prolonged in vivo survival of M. tuberculosis are summarized in Table 7.1.

A genetically determined susceptibility to mycobacterial disease due to a specific immunological deficiency has been described [1, 2]. Although known as Mendelian susceptibility to mycobacterial disease (MSMD) this entity has both clinical and genetic heterogeneity. We describe a Sri Lankan boy with recurrent and rare manifestations of mycobacterial disease in whom a complete interleukin 12 receptor defect was identified.

The marginal zone is the outer compartment of the white pulp of mammalian spleens. Most cells found in this area are intermediate-sized lymphocytes (1,2). Surface marker analyses (3–6) have provided strong evidence that these cells are B lymphocytes. Also marginal zone lymphocytes are absent from the spleens of rats treated with heterologous anti-μ antibody from birth (6). In rat spleens marginal-zone B cells outnumber the B lymphocytes found in the follicles by a factor of two to three (6,7).

The effects of a single dose of cyclophosphamide (ranging from 12 x 5 mg/m2 to 500 mg/m2) on rat spleens have been studied using quantitative morphometric techniques. The results obtained show that a single dose of cyclophosphamide (500 mg/m2) caused the destruction of primary and secondary follicles and less extensive but significant (P < 0.01) loss of small lymphocytes from the periarteriolar lymphatic sheath. Despite early changes in the small lymphocytic zone, by 10 days after drug administration the most striking feature was the depletion of lymphoid cells from the marginal zones of the white pulp.

Mycobacterium tuberculosis is a bacterial pathogen capable of survival and replication within human macrophages. Current ideas about antimycobacterial immunity grew out of the pioneering work of Lurie1 and Mackaness2. In summary, it is believed that acquired resistance to tuberculosis depends on T-cell mediated macrophage activation, resulting in an enhancement of the bacteriostatic or bacteriocidal capacity of the latter cells3. However, experimental confirmation of the above using human T-cells and macrophages has been very difficult (reviewed by Rook, 1987)4. Recent evidence indicates that murine T-cells possess cytolytic capacity against mycobacterial antigen bearing macrophages5. Adoptive transfer of such L3T4 negative Lyt-2 positive cells induces protection against intracellular bacterial infections including tuberculosis5,6. Therefore, we have investigated the generation of human T-cell lines with cytotoxic capacity against mycobacterial-antigen-pulsed macrophages.

Microfilariae found in a breast nodule of a patient with tropical pulmonary eosinophilia were identified as Wuchereria bancrofti, confirming that the tropical pulmonary eosinophilia syndrome may be associated with infections caused by this species of filarial worm.