Humoral Immune Response in Tuberculous Pleuritis

Tuberculous pleuritis is a good human model to understand the local and protective immune response against tuberculosis, due to the self-limitedness of the disease. Although the cellular immune response has been well characterised in tuberculous pleurisy, much less is known about the humoral immune response operating at the site of infection. To understand the humoral immune response, B cells were enumerated in peripheral blood mononuclear cells (PBMC) and pleural fluid mononuclear cells (PFMC) of tuberculous (TP) and non-tuberculous pleuritis patients (NTP). The levels of IgG, IgA and IgM antibodies for PPD, culture filtrate (CF) and sonicate antigens (Son Ag) were assessed in plasma (BL) and pleural fluid (PF) and a western blot was carried out with the CF antigen. The percentage of CD19+B-cells was similar in PBMC and PFMC of TP patients but was significantly lower in PFMCs of NTP patients. The IgG levels for PPD and CF antigens were higher in PF of TP than NTP patients. The antigen recognition patterns did not differ in plasma and pleural fluid of the same patient in both groups pointing out the passive diffusion of the plasma to the pleura. The antigens 25, 31, 33, 70, 110, 124 and 132 kDa were recognized exclusively by the TP patients. Thus our study showed that the local humoral response in TP did not differ from the systemic response. However, the humoral response differed in TP patients when compared to NTP patients

Role of TNF-a in host immune response in tuberculous pleuritis

Tumour Necrosis Factor (TNF)-a, a pro-inflammatory cytokine has a dual role in host immunity and immunopathology of tuberculosis and is considered to be pivotal for determining the clinical course of the disease, either beneficial or detrimental. The assessment of TNF-a in pleural tuberculosis will help us to understand its role in host defence mechanism against Mycobacterium tuberculosis (MTB) infection. In this study, TNF-a and IFN-g levels were measured in plasma and pleural fluid of both tuberculosis (TB) and non- TB patients and in the supernatants of blood and pleural fluid mononuclear cells (PBMCs and PFMCs) stimulated in vitro with PPD, culture filtrate and heatkilled (MTB). In addition, apoptosis induced by PPD and MTB was also studied. TNF-a and IFN-g were significantly elevated in pleural fluid than in plasma of pleural tuberculosis patients, suggesting the compartmentalization of Th1 cytokine-secreting cells at the site of disease. In vitro stimulation of PFMCs with PPD and MTB showed a significant increase in these cytokine levels and also enhanced apoptosis of these cells. This increase in TNF-a levels may contribute to the containment of infection by synergizing with IFN- g to activate infected macrophages or by the regulation of T-cell apoptosis

Correlates of protective immune response in tuberculous pleuritis

Tuberculous pleuritis (TB) provides a good model to study the correlates of protective immune response at the site of infection. To study the in vivo correlates of immunity, cell subset profile and cytokine assay in plasma (BL) and pleural fluid (PF) of 82 patients were done. Lymphocyte proliferation and cytokine response to mycobacterial antigens were measured in 32 subjects to understand the in vitro correlates. Increase in CD4þ cells and CD4þ/CD8þ ratio with selective concentration of interferon (IFN)-Q, tumour necrosis factor (TNF)-K and interleukin (IL)-12 in PF suggests that the CD4þ population may be of TH1 type. We observed an accelerated lymphoproliferative response to purified protein derivative (PPD) and heat killed Mycobacterium tuberculosis (MTB) in PF cells of both TB and non-TB (NTB) subjects. Interestingly, in in vitro studies, IL-4 levels together with IFN-Q were significantly increased in the supernatants of PF mononuclear cells (PFMC) of TB patients and showed a shift in immune response towards TH0/TH2 type. PPD and MTB antigens induced an enhanced proliferation of PFMC and also increased in vitro IL-4 response together with apoptosis, thus eliciting a dual response

Characterization of the protective T-cell response generated in CD4-deficient mice by a live attenuated Mycobacterium tuberculosis vaccine

The global epidemic of tuberculosis, fuelled by acquired immune-deficiency syndrome, necessitates the development of a safe and effective vaccine. We have constructed a ΔRD1ΔpanCD mutant of Mycobacterium tuberculosis (mc26030) that undergoes limited replication and is severely attenuated in immunocompromised mice, yet induces significant protection against tuberculosis in wild-type mice and even in mice that completely lack CD4+ T cells as a result of targeted disruption of their CD4 genes (CD4–/– mice). Ex vivo studies of T cells from mc26030-immunized mice showed that these immune cells responded to protein antigens of M. tuberculosis in a major histocompatibility complex (MHC) class II-restricted manner. Antibody depletion experiments showed that antituberculosis protective responses in the lung were not diminished by removal of CD8+, T-cell receptor γδ (TCR-γδ+) and NK1.1+ T cells from vaccinated CD4–/– mice before challenge, implying that the observed recall and immune effector functions resulting from vaccination of CD4–/– mice with mc26030 were attributable to a population of CD4– CD8– (double-negative) TCR-αβ+, TCR-γδ–, NK1.1– T cells. Transfer of highly enriched double-negative TCR-αβ+ T cells from mc26030-immunized CD4–/– mice into naive CD4–/– mice resulted in significant protection against an aerosol tuberculosis challenge. Enriched pulmonary double-negative T cells transcribed significantly more interferon-γ and interleukin-2 mRNA than double-negative T cells from naive mice after a tuberculous challenge. These results confirmed previous findings on the potential for a subset of MHC class II-restricted T cells to develop and function without expression of CD4 and suggest novel vaccination strategies to assist in the control of tuberculosis in human immunodeficiency virus-infected humans who have chronic depletion of their CD4+ T cells