Demonstration of MHC-specific haemolytic plaque-forming cells

Abstract

IT would be convenient to be able to measure the antibody response to alloantigens of the major histocompatibility complex (MHC) at a cellular level. As MHC alloantigens are expressed on erythrocyte membranes in mice one might suppose that a conventional Jerne plaque assay with enumeration of haemolytic plaque-forming cells (allo-PFC) against a lawn of suitable allogeneic erythrocytes would be straightforward. In fact such assays have proved difficult, with very few plaques being detected^1,2. We have found the same problem in detecting allo-PFC in the spleens of alloimmunised rats. Although alloantisera raised in appropriate strain combinations have a high titre in a direct complement dependent haemolytic assay (Fig. 1) emphasising the potential value of this convenient assay for alloantibody in the rat^3,4, very few allo-PFC were found in spleen cell suspensions from hyperimmunised donors. We show here that the discrepancy may be due to the homogeneity of the antibody product of a single PFC compared with the heterogeneity of serum antibody.