2 LYMPHOCYTE-T POPULATIONS AS EFFECTOR-CELLS FOR IGG DEPENDENT CYTOTOXICITY

The characteristics and proportions of human lymphocyte populations capable of lysing Ig[immunoglobulin]G coated target cells were studied. Monolayers of target erythrocytes coated with rabbit IgG were employed to detect and isolate the lytic effector lymphocytes. Normal peripheral blood effector lymphocytes expressed IgG receptors, and a total of 4 cell types possessing different surface markers were identified. An average of 68% (range 51-80%) of the effector lymphocytes had T [thymus-derived] lymphocyte antigen and were capable of SRBC [sheep red blood cell] rosette formation, and 32% of the lymphocytes lacked T lymphocyte markers. Two populations of these T lymphocytes were identified. One possessed SRBC and IgG receptors, and the other possessed SRBC, IgG and complement [c] receptors. The proportion of the former was estimated as 53.2% and the latter as 14.8% of the total effector cell population. Two other cell types were distinguished among the non-T lymphocytes. One type of lymphocytes bore IgG receptors (21.6%) and the other had IgG and C receptors (10.4%). The cytolytic capacity of the 2 T lymphocyte subpopulations may be an important reaction of the immune reactive T lymphocytes during the immune response.