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.