Cell-mediated immunity in rubella assayed by cytotoxicity of supernatants from rubella virus-stimulated human lymphocyte cultures.

Rubella virus-stimulated lymphocytes from rubella-seropositive donors produced in the culture medium cytotoxic activity with preferential action against rubella-infected over uninfected target cells. The ability of lymphocytes to produce the cytotoxic activity upon stimulation by rubella virus correlated with the humoral rubella-immunity status, i.e. no such cytotoxic activity developed in the supernatants of lymphocyte cultures of rubella-seronegative donors. Stimulation of lymphocytes from seropositive donors by rubella virus was also detected by thymidine incorporation, but the correlation of lymphocyte responsiveness to the humoral rubella antibody status was not so clear as in the cytotoxicity assay. Conversion of lymphocytes from unresponsive to responsive to rubella virus following natural rubella infection and after rubella vaccination was demonstrated using both methods. Following vaccination rubella-specific cell-mediated immunity first became demonstrable at 14 days. The responsiveness of lymphocytes to phytohaemagglutinin (PHA) after rubella vaccination was followed by studying thymidine uptake and the ability of lymphocytes to produce lymphootoxin. By both tests marked suppression of PHA response occurred at days 3 and 7 after vaccination.