In vitro induction of tumour-specific immunity. I. Development of optimal conditions for induction and assay of cytotoxic lymphocytes.

A microculture system for in vitro induction of tumour-specific immunity with syngeneic spleen cells and plasma-cell tumours is described. The system generates cytoxic lymphocytes assessed by their ability to lyse 51Cr-labelled target cells in a microcytotoxicity assay. Both the inductive and effector phases are subject to many variables in material and methodology and the optimal conditions are defined in this study. Of particular importance are the responder- to stimulator-cell ratios, the presence of 2-mercaptoethanol, the day of harvest, the method of target-cell 51Cr labelling, and preincubation of the cytotoxic lymphocytes prior to assay.