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

Abstract

Cells of (CBA/H BALB/c) F₁ hybrid mice express CBA/H-derived H-2^k antigens more weakly than do CBA/H ceils, 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.