Immune Response to Alloantigens of Thymus Studied in Mice with Plaque Assay

Abstract

Abstract A plaque assay in which allogeneic thymus cells were used as target antigen has been developed. Inbred mice of various strains were stimulated with an intravenous injection of 4 × 107 allogeneic thymus cells. Whenever host and donor differed in ϑ antigens, plaque-forming cells (PFC) were detected in the spleen of the host. When host and donor carried identical ϑ antigen, PFC were detected only in certain strain combinations and only at the higher immunizing dose of 4 × 108 donor thymus cells. Kinetics of the appearance of PFC was studied in the strain combinations differing in θ. In normal animals, the numbers of PFC were less than 10 per spleen. In the primary response, the peak numbers of PFC were observed in 4 to 7 days after the stimulations. In one strain combination, the mean number of PFC as high as 40,000 per spleen, was observed at the peak of the response. Marked differences in the magnitude of the PFC response to ϑ-AKR antigen were observed in various strains of mice which lack this antigen. In two strain combinations, the peak numbers of PFC were lower in the secondary than in the primary response. In one strain combination the reverse was true. Evidence was presented that PFC detected in this assay produce antibodies of IgM variety.