THE RESPONSE OF T CELLS TO HISTOCOMPATIBILITY-2 ANTIGENS : DOSE-RESPONSE KINETICS

The DNA synthetic response of a wide variety of parental thymocyte doses was studied in the lymphoid tissues of lethally irradiated F₁ mice. The response curves of the thymocytes were strikingly similar in shape to those of T cells responding to antigens, such as sheep red cells, which are more labile than the histocompatibility antigens of the F₁ host. The response was characterized by a dose-dependent latent period of 1–3 days, followed by a sharp increase in activity and a significant subsequent shutoff. Larger thymocyte doses tended to shorten the latent period. A comparison of the responses of different cell doses to one another indicated that the response usually simulated a suppressed first-order reaction. However, occasional multiple order reactions were observed. We have interpreted these data to indicate that both positive and negative interactions occur between thymocytes, without the mediation of B cell products such as conventional antibodies.