Functional and binding activity of monoclonal anti-Thy-1 antibodies: evidence for different expression of the two alleles.

Monoclonal anti-Thy-1.1 and anti-Thy-1.2 antisera selected for complement-dependent cytotoxicity have high cytotoxic and binding titers on thymocytes and peripheral T cells of mouse strains bearing the appropriate Thy-1 allele. The effect of both anti-Thy=1.1 and anti-Thy-1.2 monoclonal antisera plus complement on cytoxic T cell effectors is to abrogate their activity. On the functional activity of precursor cytotoxic T cells, monoclonal antisera against the two alleles have different effects: anti-Thy1.2 plus complement removes precursor activity of Thy-1.2-bearing strains, including (Thy-1.1 X Thy-1.2) F heterozygotes, In contrast, six different anti-Thy-1.1 monoclonals, including four of the IgM class and two of the IgG class, failed to remove cytotoxic precursor activity from the splenic T cells of AKR, A. Thy-1.1 or (CBA X AKR) F1 mice. Analysis by florescence-activated cell sorting of in vitro cultured AKR spleen cells shows that Thy-1.1 antigen appears on the cel surface during the five-day culture period.