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Biomedical subjects

D S Kumararatne

Publications and source records attributed to D S Kumararatne.

At least 19 recordsLinked to original sources
PubMed1995

CD4+ cytolytic T cells can destroy autologous and MHC-matched macrophages but fail to kill intracellular Mycobacterium bovis-BCG.

Mycobacterium bovis-BCG infected macrophages were exposed in vitro to PPD-stimulated T lymphocytes from tuberculin responsive donors or to a panel of mycobacterial-antigen specific CD4+ T cell clones. Both polyclonal and clonal T cells caused considerable antigen-specific lysis of autologous or MHC class II matched macrophages. However, lysis of infected macrophages did not significantly affect the number of viable mycobacteria which were released into the culture media from lysed macrophages. In tuberculosis, CD4+ cytolytic T cells may be primarily involved in tissue destruction and lack a significant role in acquired cellular immunity.

CD4-Positive T-Lymphocytes↗
PubMed1992

Mucosal cell-mediated immunity to mycobacterial, enterobacterial and other microbial antigens in inflammatory bowel disease.

Culture studies have suggested that Mycobacterium paratuberculosis may play a role in the aetiology of Crohn's disease. However, evidence of sensitization to mycobacterial 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 mononuclear cells (PBMC) to mycobacterial antigens. In this study we have investigated the proliferative responses of both PBMC and mesenteric lymph node mononuclear cells (MLNMC) to a range of mycobacterial and non-mycobacterial 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. paratuberculosis 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 CMI to a range of non-mycobacterial 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 pathogenesis of Crohn's disease, but indicate that further investigation may determine a role for bacterial-specific T cell-mediated responses in the pathogenesis of IBD.

Antigens, Bacterial↗
PubMed1992

An association between homozygous C3 deficiency and low levels of anti-pneumococcal capsular polysaccharide antibodies.

Inherited deficiencies of complement components are associated with an increased risk of infection by encapsulated, high grade bacterial pathogens such as Streptococcus pneumoniae, Haemophilus influenzae type b and Neisseria meningitidis. Hence, the levels of antibodies to bacterial capsular polysaccharide antigens were measured using ELISA in 65 patients with inherited deficiencies covering the classical, alternative and terminal components of the complement cascade. Three of the four C3-deficient individuals studied were found to be almost totally deficient in specific anti-pneumococcal capsular polysaccharide (PCP) antibodies. These individuals had a history of recurrent pneumococcal sepsis. While single individuals with C1r, C2 and C1Inh deficiency were found to have low anti-PCP antibody levels, no other group of complement deficiency had significantly reduced anti-PCP antibody levels compared with 100 controls. Antibody levels to the other two polysaccharides were not significantly lower in the patient groups. These findings suggest that C3 may be able to provide a stimulatory signal to promote the production of anti-PCP antibodies.

Adolescent↗
PubMed1992

Effect of blocking TNF-alpha on intracellular BCG (Bacillus Calmette Guerin) growth in human monocyte-derived macrophages.

Four agents, thalidomide, oxpentifylline, dexamethasone and a polyclonal anti-TNF-alpha antibody, were all shown by specific Elisa to block endogenous TNF-alpha production by Bacillus Calmette Guerin (BCG)-infected human monocyte-derived macrophages in in vitro culture. There was however no significant enhancement of intracellular BCG growth, over a 7-day incubation, in human monocyte-derived macrophages in the presence of any of the TNF-alpha-blocking agents, as determined by both radiometric and CFU counting methods of assessing bacterial viability and growth. The result suggests that the action of TNF-alpha alone is unlikely to be an important effector mechanism in antimycobacterial immunity within human cells.

Antibodies↗
PubMed1992

A comparison of the different methods available for determining BCG-macrophage interactions in vitro, including a new method of colony counting in broth.

Different methods of determining BCG viability based on colony forming unit (CFU) counting and radio-isotope labelling were comparatively assessed. These included radio-isotope labelling with [3H]uracil, [3H]uridine, [3H]glycerol, and CFU counting, by both agar plate dilution, and microcolony counting in broth. The sensitivity ranges of the different techniques were determined in both macrophage-free and macrophage-treated systems and used to assess the anti-mycobacterial potential of human monocyte-derived macrophages following BCG infection.

Colony Count, Microbial↗
PubMed1992

Generation of cytolytic T cells in individuals infected by Mycobacterium tuberculosis and vaccinated with BCG.

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.

BCG Vaccine↗
PubMed1990

Induction of antigen-specific CD4+ HLA-DR-restricted cytotoxic T lymphocytes as well as nonspecific nonrestricted killer cells by the recombinant mycobacterial 65-kDa heat-shock protein.

Acquired cell-mediated immunity to intracellular parasites like mycobacteria is dependent on antigen-specific T lymphocytes. We have recently found that mycobacteria not only induce helper T cells but also cytotoxic CD4+ and/or CD8+ T cells as well as nonspecific killer cells that lyse human macrophages in vitro. In addition, we have described that the recombinant heat-shock protein (hsp) 65 of Mycobacterium bovis BCG/M, tuberculosis is an important target antigen for CD4+CD8- cytotoxic T cells. We have now further investigated the cytotoxic effector cells that are induced by the hsp65 of BCG. Purified protein derivative of tuberculin (PPD)- or hsp65-specific cytotoxic T cells specifically lysed PPD, hsp65 of BCG and hsp65 of M. leprae-pulsed macrophages in an HLA-DR-restricted manner. Nonpulsed macrophages were lysed to a much lower but still significant extent. hsp65-induced effector cells expressed CD3, CD5, CD4, CD8 and CD56 markers. Depletion experiments showed that the antigen-specific HLA-DR-restricted killer cell was of the CD5+CD4+CD8-CD56- phenotype. Experiments using N-terminal truncated hsp65 fusion (cro-lacZ) proteins suggested that the N-terminal 65 amino acid residues of the 540 amino acid molecule are critical for the expression of the cytotoxic target epitope(s) in two individuals tested. In addition to inducing antigen-specific cytotoxic effector cells, the hsp65 also triggered nonspecific nonrestricted effector cells with lytic activity against nonpulsed autologous or allogeneic macrophages as well as K-562 and Daudi tumor cells. hsp65-stimulated effector cells produced both interferon and tumor necrosis factor-alpha. An important finding was that hsp65-stimulated effector cells strongly inhibited colony-forming unit formation from live BCG-infected autologous macrophages.

Antigens, Bacterial↗
PubMed1990

Specific lysis of mycobacterial antigen-bearing macrophages by class II MHC-restricted polyclonal T cell lines in healthy donors or patients with tuberculosis.

The cytolytic capacity of mycobacterial antigen-stimulated peripheral blood mononuclear cells, from healthy Mantoux-positive volunteers and from patients with tuberculosis was investigated. Polyclonal T cell lines induced by 7 days of stimulation in vitro with PPD or a sonicate of Mycobacterium tuberculosis lysed both autologous macrophages and Epstein-Barr virus (EBV) transformed B cell lines which had been pulsed with mycobacterial antigens, to a greater extent than unpulsed target cells or target cells pulsed with an irrelevant antigen (streptokinase/streptodornase). The killing of mycobacterial antigen-pulsed macrophages and EBV-transformed B cell line targets was inhibited by monoclonal antibodies to MHC class II antigens but not by antibodies directed against MHC class I antigens. PPD-pulsed EBV-transformed lymphoblastoid cell lines (LCL) competitively inhibited the killing of mycobacterial antigen-pulsed macrophages, whereas natural killer (NK) sensitive K562 cells (with or without antigen pulsing) did not inhibit mycobacterial antigen-dependent cytolysis of macrophages. Patients with tuberculosis showed a spectrum of mycobacterial antigen-induced cytolytic capacity. Those with extensive tissue necrosis (e.g. cavitatory pulmonary tuberculosis or caseous, extrathoracic tuberculosis) had high levels while patients with disseminated (miliary) tuberculosis or disease refractory to treatment showed little evidence of mycobacterial antigen induced cytotoxicity. The ability of mycobacterial antigen-stimulated lymphoblasts to kill specific antigen-pulsed autologous macrophages was not significantly different between healthy donors and patients with tuberculosis. However, the 'mycobacterial antigen-specific' component of this cytolysis was significantly deficient (P less than 0.01) in patients. We conclude that mycobacterial antigen-specific cytotoxic T cell responses may play a significant part in the immune response to mycobacterial infection.

Adult↗
PubMed1990

Selective IgG subclass deficiency: quantification and clinical relevance.

Each of the four human IgG subclasses exhibits a unique profile of effector functions relevant to the clearance and elimination of infecting microorganisms. The quantitative response within each IgG subclass varies with the nature of the antigen, its route of entry and, presumably, the form in which it is presented to the immune system. This results in antibody responses to certain antigens being predominantly or exclusively of a single IgG subclass. An inability to produce antibody of the optimally protective isotype can result in a selective immunodeficiency state. This is particularly apparent for responses to certain bacterial carbohydrate antigens that are normally of IgG2 isotype. A failure to produce the appropriate specific antibody response may result in recurrent upper and/or lower respiratory tract infection. Careful patient investigation can identify such deficiencies and suggest appropriate clinical management. In this review we outline the biology and clinical relevance of the IgG subclasses and summarize current rational treatment approaches.

Antigens, Bacterial↗
PubMed1987

Lymphocyte migration in murine malaria during the primary patent parasitaemia of Plasmodium chabaudi infections.

Inoculation of adult C57/BC mice with 10(6) red cells infected with Plasmodium chabaudi induces an acute primary parasitaemia peaking around the 8th or 9th day and lasting 10-14 days. Concomitantly, the spleen enlarges to reach 6-7 times its normal weight by the 11th day. The major component of this increase is between day 9 and 11, due primarily to an increase in erythropoietic cells in the red pulp. Although initially the white pulp increases in size, by day 11 it shows partial lymphocyte depletion which coincides with the occurrence of massive absolute lymphocytosis in the peripheral blood. 3H-Thymidine labelling in vivo suggests that this lymphocytosis is not due to lymphocytopoiesis. Collectively, these findings suggest a redistribution of lymphocytes. Lymphocyte migration was investigated around peak parasitaemia, using enriched populations of T and B cells labelled with 51Cr. The traffic patterns of these cells were followed over 36 h. These studies show decreased uptake (or decreased retention) of T and B cells by spleens of infected mice. Concomitantly, there is increased retention of T and B cells in the liver and lungs of infected mice, suggesting a complex redistribution of these cells. Lymphocyte migration to lymph nodes was unimpaired in these animals. Similar changes in T and B cell migration do not occur in Babesia microti infections in C57/BL mice. We relate our findings to histological and histochemical changes in the liver and spleen of malarious mice and discuss the significance of these findings to immunosuppression in malaria and to the development of parasiticidal immunity.

Animals↗
PubMed1984

Marginal zone B cells express CR1 and CR2 receptors.

Opsonized yeast is known to bind strongly to the marginal zones in frozen sections of rat spleen (Kumararatne, D. S. et al., Eur. J. Immunol. 1981. 11: 858). This study reports an analysis of the cells involved in this binding. Sheep red cells coated respectively with C3b, C3bi or C3d were used as indicator cells. These showed homogeneous binding of both C3b and C3bi to marginal zones and germinal centers. C3d-coated red cells bound in a uniform speckled pattern to marginal zones. They also bound to germinal centers and the small lymphocyte zones of the follicles. Selective depletion experiments were undertaken to show that binding to marginal zones was a property of the IgM+ and IgD- B cells characteristic of this area. Binding to germinal centers was attributable to follicular dendritic cells. The C3d receptors in follicles were shown to be on IgM+ and IgD+ small B lymphocytes.

Animals↗