Radioresistance of the enhancing effect of cells from carrier-immunized mice in an in vitro primary immune response.

The in vitro primary response of mouse spleen cell suspensions to 2,4,6-trinitrophenyl(Tnp)-erythrocytes has been studied. The number of anti-Tnp plaque-forming cells that arise after antigenic stimulation in vitro is greatly enhanced by prior immunization in vivo with the carrier erythrocyte. The enhancement is antigen specific. The priming for an enhanced response can be elicited with very low antigen doses and is often apparent 24 hr after immunization. It is marked from day 3 to day 14. Spleen cells from carrier-primed mice will enhance the anti-Tnp response of normal cells when mixed cultures of the two cell populations are challenged with Tnp-erythrocytes in vitro. The carrier-primed cells mediating this enhancing effect are thymus derived. The development of the thymus-derived, carrier-specific cell population has been generally assumed to involve the antigenic stimulation of cell proliferation. It was, therefore, somewhat surprising to find that the enhancing effect of the carrier-primed cells, once they had been generated, is not inhibited by x-irradiation.