Association of serum beta 2-microglobulin with H-2 class I heavy chains on the surface of mouse cells in culture.

It was found that bovine serum beta 2m binds to the H-2 class I heavy chains on the cells surface of mouse L cells during cultivation of the cells in medium supplemented with fetal calf serum (FCS). This conclusion is based on the following observations. 1) Syngeneic C3H antisera against mouse L cells in culture with FCS (anti-L-FCS sera) were found to react with the 48K and 12K dalton molecules on the mouse L cells. 2) When mouse L cells were cultured in medium supplemented with mouse serum or human serum, the anti-L-FCS sera did not detect any molecule on the L cells. 3) The anti-L-FCS sera immunoprecipitated bovine class I antigen on mono-nuclear cells from a cow. Two-dimensional (2-D) gel electrophoresis showed that the heavy chain detected by anti-L-FCS sera on the mouse L cells in culture with FCS was identical to the mouse H-2 class I heavy chain, but the light chain was identical to the bovine beta 2m. 4) Anti-H-2Kk and anti-H-2Dk sera detected bovine beta 2m in association with H-2 class I antigens on mouse L cells. The association of serum beta 2m and mouse class I antigens was further examined by 2-D gel electrophoresis by using combinations of normal mouse lymphocytes and FCS, or of mouse L cells and human serum, or of mouse L cells and C57BL/6 mouse serum. The results indicate that H-2 antigen does not have an additional binding site for serum beta 2m other than that for light chain. In addition, the results suggest that the light chains of H-2Kk and H-2Dk antigens have different reactivities to anti-beta 2m antibody from each other, probably due to a difference in configurations of their molecules.