Mycobacterial antigen-specific human T-cell clones secreting macrophage activating factors.

Macrophage activating factor (MAF) is produced by antigen-stimulated lymphocytes and activates macrophages for antimicrobial function. The capacity of individual microbial antigens to evoke and regulate this response has been explored using an affinity purified antigen (TB68) of Mycobacterium tuberculosis in combination with T-cell cloning. Four helper/inducer clones are described which responded strongly to this antigen. Three were specific, proliferating only to TB68 antigen and antigenic preparations containing this antigen. However, one of these clones (68.1) did not proliferate to BCG and PPD which contained the TB68 antigen. In addition, another clone, 68.13, also proliferated to other antigenic preparations which did not contain the TB68 antigen. Taken together, these data indicate the presence of several epitopes in the affinity-purified TB68 antigen. All the clones produced MAF, which enhanced H2O2 production in U937 cell lines and conventional macrophages matured from monocytes. Thus, T-cell clones proliferating to a mycobacterial antigen constitutively secrete lymphokines that activate macrophages to antimicrobial immunity.