Inhibition of anti-class I cytotoxicity by anti-class II monoclonal antibodies (MoAb). II. Blocking of anti-class I CTL clones by anti-DR MoAb.

Monoclonal antibodies directed at monomorphic determinants on A,B,C (w6/32) or DR (L243, S4/24, S8/8) HLA antigens were used to inhibit the cytotoxic activity of class I- or class II-reactive CTL clones. Anti-class I (HLA-Bw62) cytotoxic T lymphocyte CTL clones were inhibited by w6/32, but not by L243, when tested on PHA blasts and LCL as targets. Interestingly, S4/24 and S8/8 demonstrated a differential blocking ability of class I reactive clones; these two monoclonal antibodies could not block Bw62-directed CTL clones when using PHA blasts as targets but strongly inhibited the cytotoxic activity of the same clones on LCLs as targets.