In vitro measurement of human T cell responses to varicella zoster virus antigen.

Means to quantitate cell-mediated immunity are increasingly in demand as modifications to existing vaccines and new vaccines are tested. For immunity to varicella zoster virus, there is over a decade of experience with estimates of responder cell frequency obtained by diluting the number of lymphocytes in antigen-stimulated cultures. This method shows substantial variations between subjects, so populations of 12 or more subjects per group are needed to make comparisons possible. Cytokine-based methods for T lymphocyte responses may prove more sensitive, as may direct antigen-binding methods using tetramers of peptide and histocompatibility antigens--but experience with both is very limited.