H-2 antigen variants in a cultured heterozygous mouse leukemia cell line. VII. Effect of selection with a hybridoma antibody.

An (H-2k/H-2d)F1 sarcoma cell line was subjected to immunoselection using ascites fluid from a mouse growing a hybridoma secreting an anti H-2Kk antibody.One hundred random clones were picked from the surviving population and screened by direct cytolysis using the hybridoma antibody or alloantisera against H-2Kk and H-2Dk. Fifty-nine clones were resistant to all three antisera, indicating that they no longer expressed the entire H-2k haplotype. Thirty-two were resistant to the ascites and to the anti H-2Kk alloantiserum, but sensitive to the anti H-2Dk serum, indicating that they had lost H-2Kk antigen, but retained H-2Dk. Nine clones were sensitive to the alloantisera, but resistant to the hybridoma, indicating that, though they retained the product(s) recognized by the alloantiserum against H-2Kk, they had lost the site(s) that bound the hybridoma antibody. Quantitative absorption assays using lymph-node cells from young BALB.K (H-2Kk) mice as targets show that one representative clone from the last group absorbs the anti H-2Kk activity in the alloantiserum. This implies that the sensitivity of the variant clone to the alloantiserum is not due to contaminating anti C-type virus antibodies in the serum. The possible implications of these data are discussed.