Fc-receptor-bearing cells in spleen of mice injected with cell-free Ehrlich ascites fluid (EAF).

The kinetics of different cell populations (T and B) and subpopulations (one bearing easily releasable FcR and one bearing stable FcR) was followed in spleens of mice after one single i.p. injection of EAF. The number of FcR bearing cells doubled within 2-7 days after EAF injection. This increase was due to cells bearing temperature sensitive FcR and was accompanied by the doubling of theta positive cells. These results, supported by the demonstration of doubly labeled (theta+FcR+) cells, suggest that EAF injected into normal mice causes the appearance of T-cells expressing easily releasable FcR. These cells, according to Fridman et al. (1977) are suppressor cells. Maximal increase of theta positive cells and of cells with temperature sensitive FcR detected in vitro coincided with the maximum of the suppressive activity of EAF detected in vivo.