Delayed hypersensitivity to soluble antigens in mice. II. Analysis in vitro.

Delayed hypersensitivity to a soluble protein has been analyzed in vitro with lymph node cells from mice. Antigen-dependent cytotoxicity against innocent bystander cells, and incorporation of tritiated thymidine have been used to monitor the response to a subcutaneous tail injection of egg albumin (OVA) in complete Freund's adjuvant. Sensitized lymph node cells from mice with positive 24 h ear tests killed A9 cells in the presence of antigen. This antigen-specific, T cell-mediated cytotoxicity was observed within 4 days of sensitization and still apparent at 7 months. Reactivity to OVA, assessed as an increase in DNA synthesis in the presence of antigen, was also T cell dependent and exhibited similar sensitization kinetics and dose requirements. Both microtechniques require as few as 10(5) lymphocytes and are readily adaptable to the study of delayed hypersensitivity to any soluble protein in mice.