Antibody Production by Host Cells in X-Irradiated Recipients of Allogeneic Spleen Cells

Abstract

Experiments were performed to test the hypothesis that two different cells, a radiosensitive antigen reactive cell and a radioresistant precursor of the antibody producing cell collaborate in antibody synthesis. Twenty-four hours following 500 R x-irradiation, experimental recipient group C mice were injected with normal allogeneic spleen cells and sheep red blood cells (SRBC). Control recipients of group A were irradiated similarly and injected with SRBC alone while control recipients of group B were irradiated similarly and injected simultaneously with SRBC and allogeneic spleen cells from heavily irradiated (1000 R) mice. Five to 10 days after antigen injection, the numbers of plaque-forming cells (PFC) of donor and host origin were determined in the spleens of the three groups. The contribution of donor and host PFC was distinguished by the use of anti-histocompatibility sera. On day 5, the spleens of mice in group C contained 26 times as many PFC as did the spleens of mice in group A. Of these, 80% were donor cells and 20% were of host type. Thus more than five times as many host PFC developed in group C than in group A. At least some of the stimulatory effect on host PFC was independent of the normal donor spleen cells because the spleens of control group B contained twice as many PFC as did those of control group A. On days 6 and 7, the PFC in group C decreased, while those in control group A increased, possibly due to alloimmune reactions between donor graft and recipient. The injection of antidonor H-2 serum into group C on day 3 suppressed the development of PFC of both donor and recipient type. Evidently survival of donor cells beyond day 3 was necessary for the enhanced recipient PFC response. It is concluded that existing data establish the importance of cell interactions in the immune response but do not prove the existence of an antigen-sensitive cell capable of transmitting antigen-specific information to the precursor of the antibody-producing cell.