Presence of host-reactive T cells in lymphohaematopoietic chimeras.

The presence of autoreactive lymphocytes was investigated in murine lymphohaematopoietic chimeras. In this report we demonstrate the presence of precursors of host-reactive cytotoxic effector T lymphocytes in parent leads to F1 chimeras. Lymphocytes from these chimeras display cytotoxic activity towards the non-shared major histocompatibility complex (MHC) antigens of the host following activation with the polyclonal T-cell activator concanavalin A. These host-reactive cells were found despite the apparent absence of lymphocytes demonstrating autoreactivity in other experimental systems: mixed lymphocyte reaction, cell-mediated lympholysis, positive allogeneic effect and negative allogeneic effect. Animals possessing precursors of these cytotoxic effector cells also possess precursors of cytotoxic effector cells capable of generating an MHC-restricted anti-minor histocompatibility antigen response. The results are discussed in reference to the role of the thymus in effecting self non-self discrimination.