Intracellular granzyme A expression of peripheral blood lymphocyte subsets in pulmonary tuberculosis.

Vidyarani, M.; Selvaraj, P.; Jawahar, M.S.; Rajeswari, D.N.; Anbalagan, S.; Narayanan, P.R.

Current Science; 2007; 93; 823-825.

Abstract: Cell-mediated immunity is a key weapon of host defence against tuberculosis (TB). Granzyme A (GzmA), a serine protease, present in the granules of cytotoxic cells induces caspase-independent cell death. We estimated the proportion of GzmA producing lymphocyte subsets in peripheral blood from 59 normal healthy volunteers and 48 pulmonary TB (PTB) patients using flow cytometry. When compared with normal healthy subjects, we observed a significantly higher percentage of GzmA-positive CD56 + cells ( P = 0.01) in PTB patients. However, when the absolute number was compared between the two groups, a significantly decreased number of GzmA-expressing CD16 + ( P = 0.01) and CD56 + ( P = 0.0001) cells was observed in patients and this could be explained by the significantly reduced number of total lymphocytes ( P = 0.0009) seen in the patients. There was no significant difference in the number of CD4 + and CD8 + GzmA double-positive cells between the two study groups. CD56 is a natural killer cell marker and these cells represent innate immune response to TB. We report an increased percentage of CD56 + cells expressing GzmA in TB patients, which shows the relevance of the GzmA-mediated pathway of apoptosis in immunity against Mycobacterium tuberculosis.

Keywords: Cytotoxic cells, granzyme A, peripheral blood, pulmonary tuberculosis.

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