ABSTRACT
This study was done to comparethe lymphocyte subpopulations in the peripheral blood of patients of acid fast bacilli positive active pulmonary tuberculosis with similar patients who were negative for acid fast bacilli on sputum examination. After exposure to Mycobacterium tuberculosis, only 15% of the infected individuals develop active tuberculosis while about 90% can control and contain the infection successfully. This ability to control the infections is the function of T lymphocytes. Different profiles of lymphocyte subpopulation possibly reflect the immune status of the individual against tuberculosis infections. This study was carried out to compare the lymphocytes subpopulations in the peripheral blood of patients of AFB negative tuberculosis. A total of forty adult patients of pulmonary tuberculosis having positive sputum smears for acid fast bacilli along with fifteen acid fast bacilli negative patients were included in the study. Peripheral blood samples from the patients of both groups were collected aseptically in EDTA containers. A panel of monoclonal antibodies was used to delineate different lymphocyte subsets by flow cytometry. Haemoglobin levels, total leucocyte counts, absolute neutrophil counts and absolute lymphocyte counts were determined by haematology autoanalyser. Total CD4 count was not significantly different in the two groups but activated CD4+ T cell number was significantly high in smear positive patients. Smear positive patients also showed significantly increased total number of CDS positive T lymphocytes but activated CDS lymphocyte number was significantly decreased. Total number as well as activated fraction of gamma dejta T cells was markedly enhanced in smear negative group of patients. Activation status of CD8+ T lymphocytes along with increased number of gamma delta cells [absolute number as well as activated fraction] make important contributions in limiting the extent of disease in pulmonary tuberculosis