Studies on thymocyte subpopulations in guinea pigs. IV. A subpopulation sensitive to a natural, cold reactive cytotoxic factor in autologous serum.

Guinea pig serum was shown to be cytotoxic against a subpopulation of autologous thymocytes. The sensitive cells belonged to the population of small, high-density cells, constituting the majority of cortical thymocytes. In this respect, the activity resembled that of some heterologous sera tested (rat, rabbit) and allogeneic serum. The same population was also particularly reactive in rapid early (RE) migration [Sandberg, 1981] induced by rat serum. Human serum differed from other tested sera both as regards cytotoxicity and RE migration. The cytotoxic effect of autologous serum was demonstrated at 4 degrees C, whereas it was absent at 37 degrees C. The latter is in contrast to the cold reactive thymocytotoxic autoantibodies previously described in some mouse strains, and it is also in contrast to thymocytotoxic factors in heterologous serum. In all tested sera, the activity was completely inhibited by incubation at 56 degrees C for 30 min. The results may be relevant for the understanding of normal cell death in the thymus, and are discussed in relation to lymphocytotoxic autoantibodies in various disease states in man and animals.