In Vitro Cytotoxicity of Human Lymphocytes: Reduction of the Lymphocyte Cytotoxicity Induced by Antibodies or Phytohemagglutinin by Removing Immune-Complex-Binding Cells

Immune-complex-binding cells have been excluded from suspensions of purified human lymphocytes by a rosette-formation procedure with antibody-sensitized ox erythrocytes. After such treatment the remaining lymphocytes were tested in a cytotoxicity assay, using ⁵¹Cr-labeled chicken erythrocytes as the target cells. Lymphocyte cytotoxicity for antibody-coated target cells was profoundly reduced after removal of immune-complex-binding cells (more than 10 times reduction within 4 to 6 hours of incubation). Lymphocyte cytotoxicity induced by phytohemagglutinin (PHA) was also reduced by the same procedure. This reduction was less marked, the cytotoxicity of lymphocytes lacking immune-complex-binding cells being 26% to 82% (mean, 47%) of control lymphocytes. The results indicate that a population of immune-complex-binding lymphocytes is needed for lymphocyte cytotoxicity induced by target cell antibodies and also for the full expression of PHA-induced cytotoxicity.