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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.

The global epidemic of tuberculosis, fuelled by acquired immune-deficiency syndrome, necessitates the development of a safe and effective vaccine. We have constructed a DeltaRD1DeltapanCD mutant of Mycobacterium tuberculosis (mc(2)6030) 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 mc(2)6030-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 gammadelta (TCR-gammadelta(+)) 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 mc(2)6030 were attributable to a population of CD4(-) CD8(-) (double-negative) TCR-alphabeta(+), TCR-gammadelta(-), NK1.1(-) T cells. Transfer of highly enriched double-negative TCR-alphabeta(+) T cells from mc(2)6030-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-gamma 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.

We report the safety and immunogenicity of a double lysine and pantothenate auxotroph ofMycobacterium tuberculosisin mice. The ΔlysAΔpanCDmutant is completely attenuated in immunocompromised SCID and gamma interferon knockout mice yet induces short-term and long-term protection in immunocompetent and CD4-deficient mice following single-dose subcutaneous vaccination.

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 CD4(+) cells and CD4(+)/CD8(+) ratio with selective concentration of interferon (IFN)-gamma, tumour necrosis factor (TNF)-alpha and interleukin (IL)-12 in PF suggests that the CD4(+) 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-gamma 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.

Differential T helper cell response in tuberculous pleuritis. Prabha, C.; Jalapathy, K.V.; Matsa, R.P.; Das, S.D. Indian Journal of Medical Microbiology; 2007; 25; 18-23. Purpose: This study was conducted to understand the in vivo and in vitro immune responses and to find whether there exists any difference in the systemic and localized immune responses in tuberculous pleuritis. Methods: The in vivo levels of IFN- g and IL-4 were compared in plasma (BL) and pleural fluid (PF) of 47 tuberculous (TB) and 31 nontuberculous pleuritis (Non-TB) patients. In vitro cytokine response to various mycobacterial antigens was studied in 19 TB patients by ELISA. Both ex vivo and in vitro cytokine responses were further ascertained by intracellular cytokine staining on purified CD4 + T cells from pleural fluid mononuclear cells (PFMC) of 10 TB paitents. Results: The ex vivo results showed a significant increase in IFN- g levels and higher IFN- g + T cells in PF. On the other hand, in vitro results showed simultaneous increase in both IFN- g and IL-4 levels in the supernatants of antigen stimulated PFMC. Similarly antigen specific increase was observed in both IFN- g + and IL-4 + T cells in all cultured conditions. However, the percentile increase was more in IL-4 secreting T cells, significant for PPD stimulation ( P< 0.05), indicating that in vitro cellular response was dominated by Th2 type. Conclusions: These results showed a differential T–helper response in TB pleuritis suggestive of predominant Th1 in vivo and mixed response (Th1 and Th2) under in vitro conditions.