Cell‐Mediated Lympholysis after Sensitization in Unidirectional Mixed Lymphocyte Culture in Man

Abstract

The cytotoxicity of human peripheral blood lymphocytes (PBL), after a 6‐day allogeneic stimulation in unidirectional mixed lymphocyte culture (UMLC). was studied. PBLs stimulated with phytohemagglutinin (PHA) and labeled with 51 Cr were used .as target cells. The effector cells were incubated with the target cells at I 100:1 ratio for 6 In. The amount of isotope released into the supernatant was used to calculate lysis. Cell‐mediated lympholysis (CML) was specific, as shown by an innocent‐bystander experiment and by the lack of lysis of target alls autologous with the effector cells. The specific lysis had the following features: linear increase between 2 and H hr of incubation, linear increase with the logarithm of the number of effector cells, and inhibition by EDTA and by cytochalasm B. Under the UMLC conditions used, potent effector cells were present already on day 4. A reduction in the number of stimulating cells to one third of the number of responding Cells in UMLC resulted in a decrease of thymidine incorporation and in an increase of CML. The significance of CML for transplantation biology is discussed.