Role of the thymus in generation of lymphocyte functions. I. Demonstration of lymphocytes reactive to mitogens and allogeneic cells in the embryonic mouse thymus in organ culture.

The thymuses of 14-day-old CBA mouse embryos cultured for 14 days in organ cultures supplemented with mouse serum contained lymphocytes that were highly reactive to the mitogens concanavalin A (Con A) and leukoagglutinin (LA) and to irradiated allogeneic spleen cells in vitro. In contrast, thymocytes derived from fetal-calf-serum-supplemented organ cultures displayed much weaker responses to the two mitogens and little or no response to the allogeneic spleen cells. Control thymocytes obtained from 1-month-old CBA mice responded well to Con A but not to LA. The responses of these cells to allogeneic spleen cells were delayed compared with the organ-culture-derived cells, which responded promptly, with a maximum already on culture day 2-3. The results demonstrate that the organ culture system provides a convenient model for further study of the generation of immunoreactive cells in the mouse thymus.