Antibody and lymphocyte responses to Mycobacterium tuberculosis culture filtrate antigens in active and quiescent (cured) pulmonary tuberculosis.

Humoral and lymphocyte responses to Mycobacterium tuberculosis culture \nfiltrate antigens were studied in active pulmonary tuberculosis (ATB) cases (n = 62), \ninactive (cured/quiescent) tuberculosis (ITB) patients (n = 62) and healthy control \nsubjects (n = 60). \nActive tuberculosis patients showed very high antibody titre to M. tuberculosis culture \nfiltrate antigens as compared to ITB and control subjects. M. tuberculosis antigens from \n17 to 80 kDa were recognised by the plasma of all ATB and ITB patients as well as \ncontrol subjects. However, the 38, 32-34, 30-31 and 27 kDa antigens were recognised \nmore by the ATB patients as compared to the control subjects while the 64/66 kDa \nantigen was mostly recognised by the cured patients. Increased lymphocyte responses \nwere seen with increasing concentrations of M. tuberculosis culture filtrate antigens and \nmitogens such as Phytohaemagglutinin (PHA) and Concanavalin-A (Con-A) in ATB and \nITB patients as well as healthy control subjects. However, a low or suppressed \nlymphocyte response to PHA, Con-A and M. tuberculosis culture filtrate antigens was \nseen in ATB patients compared to ITB patients and control subjects. \nThe study suggests that during the active stage of the disease, the humoral immune \nresponse is augmented but the antigen and mitogen induced lymphocyte response (an in \nvitro correlate of CMI response) is suppressed. This further suggests that the humoral \nimmune response regulates the CMI response during the active stage of the disease; \nwhen the disease is cured, the antibody response declines and the lymphocyte response \nto antigens and mitogens increases to the same level as found in controls. This suggests \nthat normal immune status gets restored in cured patients.