Cyclophosphamide induction of splenic suppressor cells in hamsters

Injection of hamsters with a single sublethal dose of cyclophosphamide induced splenic atrophy followed by considerable hypertrophy. During the splenomegaly phase, the in vitro reactivity of spleen cells to concanavalin A (ConA) or protein A (ProtA) was decreased. The spleens of 6-8-month old animals contained cells able to suppress the in vitro reactivity of normal lymphocytes to ConA or ProtA. These cells were absent in 2-month old animals, and some suppressor activity could be shown in 3-month old hamsters. Suppressor activity was abolished by removal of adherent cells and by silica treatment, but antisera against thymocytes or IgG were ineffective.