Cytotoxicity of temporarily adherent human mononuclear blood cells. 2. Characterization of effector cells.

In monolayers of freshly isolated human mononuclear blood cells, 5-10% of the adherent cells are non-monocytic. These cells detach during the first day of in vitro culture. These detached cells exert high cytolytic and cytostatic activities. The detached cells were found to be mostly (90%) nonmonocytic as assessed by cell morphology studies and characterization with respect to membrane markers. The detached cells consisted of 40% T-lymphocytes. 10% B-lymphocytes and 40% non-T, non-B lymphocytes. Thirty-five percent of the cells were Fc-receptor-bearing cells. Following sheep red blood cell (SRBC) rosetting, the cytotoxic cells were found in the non-SRBC-rosetting fraction, viz. they were non-T lymphocytes.