Broad clonal heterogeneity of antigen-specific CD4+ T-cells localizing at the site of disease during tuberculosis.

The repertoire of CD4+ T-lymphocytes was investigated in six patients affected by tuberculosis, who had a negative PPD skin test at diagnosis. Polyclonal CD4+ T-cell lines from the peripheral blood failed to proliferate to PPD and to the 16- or 38-kDa proteins of Mycobacterium tuberculosis, while CD4+ T-cell lines from the site of disease responded to PPD, and to the 16- and 38-kDa proteins, and derived epitopes in vitro. The repertoire of CD4+ T-cells accumulating at the site of disease was found to be widely heterogeneous as demonstrated by the finding that at least seven different peptides from the 16- and 38-kDa proteins were recognized by every patient. These results indicate that CD4+ T-cells localized at the site of disease in tuberculosis recognize a vast array of M. tuberculosis epitopes.