Nature of T-cells resident in spleens of thymectomized,lethally irradiated,bone marrow-reconstituted mice

Adult thymectomized, lethally irradiated, bone marrow-reconstituted (ATxXB) mice that had been weakly primed with SRBC or HRBC between thymectomy and irradiation were shown to retain antigen-specific immunological memories for at least 1–5 months after bone marrow reconstitution. This could be shown by anamnestic antibody response in vivo as well as by proliferative response of the spleen cells to the test antigens in vitro. Spleen cells taken from ATxXB mice showed a reduced but significant proliferative response to nonspecific T-cell mitogens, in particular to Con A, in vitro. Treatment of the donor bone marrow cells used for reconstitution of ATxXB mice with anti-Thy 1.2 sera + C′ did not affect the generation of immunological memories nor the magnitude of the proliferative response of spleen cells to nonspecific T-cell mitogens in vitro, indicating that the cells responsible for such functions were host derived. Finally, the antibody-forming capacity of spleen cells derived from SRBC-primed ATxXB mice to the test antigen in vitro was completely abrogated by exposure to 450 R, whereas the helper function of the same cell suspension remained unaffected even after exposure to 1000 R. Implication of these findings on the nature of T cells resident in spleens of ATxXB mice was discussed.