Primed avian gamma delta T cells respond to mycobacterial antigens, but show no preference for the 65-kDa heat shock protein.

We have studied the reactivity of chicken T cells to mycobacterial antigens. Neither peripheral blood nor splenic lymphocytes isolated from unprimed chickens proliferated in response to mycobacterial antigens (mycobacterial sonicate, purified protein derivative, or recombinant 65-kDa heat-shock protein HSP65). After immunization with complete Freund's adjuvant (CFA) a strong response appeared, and a transient increase of peripheral blood gamma delta T cells was observed. Analysis of spleen cells isolated from CFA-primed chickens showed that both alpha beta and gamma delta T cells were activated by the mycobacterial antigens, apparently at equal levels. Both subsets also responded to HSP65, but no preference of gamma delta T cells to respond to it or any of the other mycobacterial antigens was observed. These results indicate that although HSP65 is an important mycobacterial antigen, it is not dominant in the chicken gamma delta T cell repertoire. Moreover, the results show a clear distinction between the naive and primed repertoire of gamma delta T cells.