Recovery of Immune Responsiveness in Lethally-irradiated Mice Protected with Syngeneic Marrow Cells

Abstract

Recovery of antibody-forming capacity in the spleen of lethally-irradiated mice protected with 10⁶ syngeneic marrow cells has been examined in terms of the recovery of PFC responsiveness to Srbc and its sensitivity to thymus cell influence, and secondly in terms of the recovery of focus-forming capacity. PFC responsiveness was not detected for almost 2 weeks after irradiation and grafting. This was followed by a biphasic recovery pattern. Both PFC and focus-forming capacity increased rapidly during the next 1 to 2 weeks and then subsequently much more slowly. Injection of 50 × 10⁶ normal thymus cells into mice at the time of immunization resulted in an apparent hastening of the recovery of PFC responsiveness. The possibility that the observed recovery pattern reflects an impaired production of thymus-derived antigen-reactive cells is discussed.