| Abstract: | T lymphocyte clones reacting specifically with the antigenic components of Eimeria tenella were generated from splenic lymphocytes of immunized chickens and were maintained for 12 to 14 wk in vitro. These T cell growth factor-dependent T lymphocyte clones from bursectomized and normal chickens proliferated in vitro when stimulated with antigens from different developmental stages of homologous but not heterologous species of the parasite. Specific proliferative responses of the cloned T cells showed an absolute requirement for antigen presentation by histocompatible antigen-presenting cells. Some of the T cell clones exhibited functionally discrete interactions with syngeneic primed B cells; 25% of the T cell clones from immunized normal chickens and 7% of those obtained from immunized bursectomized chickens showed antigen-dependent helper activity and induced specific antibody production by syngeneic primed B cells. Of the T cell clones from immunized normal chickens, 19% showed suppression of in vitro antibody production in comparison to 7% of those isolated from immunized bursectomized chickens. The frequency of cloned T cells with ability to induce cytotoxic activity in macrophages against the sporozoites of E. tenella was much higher in those isolated from bursectomized chickens (80%) than in those isolated from normal chickens. Because both bursectomized and normal chickens can be immunized by repeated infections, differences in the distribution among cloned T cells suggest different effector mechanisms of immunity against coccidiosis in these chickens. Lack of B cells seem to affect the development of T cell immunity as reflected by slower development of immunity and enhanced activation of cytotoxic T cell function. |
