Local immunodiagnosis of pulmonary tuberculosis by enzyme-linked immunospot

Lymphocytes are crucial in the immune defence against Mycobacterium tuberculosis (MTB) infection. The aim of the present study was to ascertain whether or not MTB-specific lymphocytes are selectively compartmentalised in the lungs of patients with minimal active pulmonary tuberculosis (PTB). Patients with smear-negative MTB-culture-confirmed PTB were prospectively recruited. Differential cell counts, immunophenotyping with monoclonal antibodies directed against the cell surface markers CD4, CD8, CD4CD45RA, CD4CD45R0, CD38, human leukocyte antigen DR, CD19, CD3, CD57 and CD16 and MTB-specific enzyme-linked immunospot assays of peripheral blood mononuclear cells and bronchoalveolar lavage (BAL) mononuclear cells with 6-kDa early secretory antigenic target and culture filtrate protein 10 were performed. Among 12 patients with culture-confirmed smear-negative PTB, no differences were found in the distribution of total CD4 or CD8 T-cells in peripheral blood or BAL fluid (BALF). Activated human leukocyte antigen-DR-positive cells, as well as memory CD4CD45R0-positive T-cells, were expanded among cells of the BALF. Compared with a group of control patients with alternative pulmonary pathologies, there was no significant difference in lymphocyte subpopulations. However, 6-kDa early secretory antigenic target- and culture filtrate protein 10-specific lymphocytes were more concentrated, with a median BALF:peripheral blood ratio of 9.9 and 8.9, respectively, in patients with PTB. Mycobacterium tuberculosis-specific T-cells are highly selectively compartmentalised at the site of infection in active pulmonary tuberculosis.