Identification of the Cell Population Involved in Viral-Specific Cell-Mediated Cytotoxicity in Man: Evidence for T Cell Specificity

The nature of the cell population involved in lymphocyte-mediated cytotoxicity to baby-hamster-kidney (BHK-21) target cells persistently infected with rubella virus was investigated by a 51 Cr-release microassay. After depletion of the T cell population with an antiserum to human-thymus-lymphoid tissue antigen (HTLA), the purified B cell population showed a decrease in E-rosette formation (9.0 ± 2.2% compared to 69.6 ± 9.1% before treatment) and an insignificant degree of cytotoxic activity against rubella-infected target cells (specific immune release of 51 Cr was 0.9 ± 2.6% compared to 24.2 ± 3.8 before treatment). A purified T cell population, prepared by depletion of B cells with an anti-human immunoglobulin serum and complement, was found to show no alteration in E-rosette formation (85.2 ± 6.2%) or cytotoxicity (30.3 ± 4.4% SIR) but showed decreased EA- and EAC-rosette formation (2.7 ± 1.5% and 10.5 ± 3.2%, respectively, compared to 19.4 ± 2.9% and 28.0 ± 4.1% before treatment). A monocyte-depleted population prepared by removal of the plastic adherent mononuclear cells showed no significant alteration of rosette formation or cytotoxicity. These experiments suggest that the predominant lymphoid population responsible for direct cell-mediated cytotoxicity to virus infected target cells in the 51 Cr-release microassay appears to be effected by a thymus-dependent lymphocyte population.