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
