Ultrastructure of lymphocyte-mediated cytotoxicity. I. Interaction between phytohaemagglutinin-stimulated human lymphocytes and chicken erythrocytes.

Summary. The ultrastructural appearances of the interaction between normal phytohaemagglutinin (PHA)-stimulated human lymphocytes and chicken red cells (ChRBC) were studied. Close contact between ChRBC and control non-stimulated lymphocytes was often observed indicating that this is a non-specific phenomenon. In mixtures of PHA-stimulated lymphocytes and ChRBC, time-dependent development of interdigitating pseudopods between the two cell types was observed which was not seen in controls. Their development followed the same time-course as release of 51Cr when the ChRBC were pre-labelled with this marker. The findings suggest a relationship between the morphological changes observed and the destruction of the target cells (ChRBC).