Adoptive transfer of cell mediated immunity is a widely acknowledged long term goal (NIAID). Our studies focus on aspects relevant in the context of severe or progressive herpesvirus infections in patients with secondary immunodeficiency: how can T cells of defined specificity be cultured in vitro, what are the requirements of different T and NK cell subsets for help and how can their function be characterized? VZV is selected as the model herpesvirus because it is clinically important in immunosuppressed subjects. The approach will be: 1. stimulate blood mononuclear cells (MNC) from healthy donors with VZV presented as extracted antigen on autologous monocytes, or as VZV infected fibroblasts or lymphoblasts, HLA matched with the responder T cells for class I or class II major histocompatibility (MHC) antigens. Responding T cells will be phenotyped by monoclonal antibodies to define optimal conditions for responses by individual subsets. 2. Deplete MNC of monocytes or single T subsets to determine whether different responder subsets have different accessory or helper cell requirements. 3. Cells from stimulated cultures will be tested for MHC restricted cytotoxicity using the fibroblast and lymphoblast targets as these differ in their VZV as well as MHC antigen expression. 4. T cells from cultures stimulated under conditions defined in 1 will be cloned and tested for (a) cytotoxicity (b) help for in vitro antibody production and (c) IL 2 production. 5. The possible recognition of different VZV antigens by MHC class I or II restricted T cells will be tested by proliferation or cytotoxicity inhibition by VZV glycoproteins isolated by affinity chromatography. 6. The development of VZV immunity in healthy subjects receiving VZV immunization will be followed (a) for comparison with immunity to wild type VZV and (b) to provide a reference group for responses in elderly subjects before and after booster immunization. Or studies would provide a detailed view of immunity to a clinically important virus, VZV, and the means for culturing functionally restricted VZV specific T cells.