VARIATION IN H-2-ANTIGEN EXPRESSION IN F1-HYBRID MICE - ANALYSIS USING MONOCLONAL-ANTIBODIES

Cells of (CBA/H x BALB/c) F1 hybrid mice express CBA/H-derived H-2(k) antigens more weakly than do CBA/H cells, but H-2(d) antigens are similarly expressed by F1 and BALB/c cells. This was evident when F1 hybrid macrophages were compared with CBA/H and BALB/c macrophage as targets for both alloreactive and H-2 restricted antiviral Tc cells. Quantitative absorption of anti-H-2K(k) serum by spleen cells of F1 or CBA/H mice also suggested about 3-fold less H-2K(k) antigen on F1 cells. With the use of two anti-H-2K(k) monoclonal antibodies, 30R3 and 27R9, the reduced expression of H-2K(k) in this F1 hybrid was further analysed in a two-stage radio-immunoassay employing the uptake of 125I-protein A to measure antibody binding. By a thermodynamic approach, estimates were made of the dissociation constant for antibody binding, and of the relative numbers of H-2 molecules expressed by both F1 hybrid and CBA/H spleen cells. The results indicate that there is a two-fold reduction in the number of H-2K(k) molecules expressed on the surface of F1 cells. Similar dissociation constants for F1 and CBA/H cells indicated no detectable qualitative difference in their H-2K(k) antigens with respect to sites recognized by 30R3 and 27R9.