HLA-DR expression on cytotoxic T lymphocytes.

A DR-null and DQ-null mutant lymphoblastoid cell line (LCL) was used to generate cytotoxic T cells (CTL) to investigate DR expression on CTL. Effector T cells generated in human allogeneic mixed lymphocyte culture (MLC) were separated on a fluorescence-activated cell sorter (FACS) into DR-positive and DR-negative subsets. The great majority of detectable cytolytic activity, anti-class I and anti-class II (presumably anti-DP) CTL, as well as natural killer (NK)-like activity, resided within the DR-positive population.