The broad long-term objective of the proposed research is to gain insight into the biological role of gammadelta TCR bearing lymphocyte subsets. The studies proposed include the following specific aims: 1. To characterize in molecular terms Major Histocompatibility Complex (MHC) class I or similar molecules capable of presenting HSP-60 peptide antigens to mouse gammadelta T cells. Our preliminary data indicate a requirement for MHC class I or similar molecules in the recognition of HSP- 60 derived synthetic peptide antigens by gammadelta T cell receptor (TCR) bearing hybridoma cells. We not propose a combined approach using mouse genetics and molecular cloning techniques to identify these putative antigen presenting molecules. 2. To isolate and characterize in molecular terms naturally processed peptide ligands that are specifically recognized by HSP-60 reactive gammadelta T cells. HSP-60 reactive gammadelta TCR bearing hybridoma cells can be stimulated with acid soluble, low molecular weight and protease- sensitive material derived from the same cells. We propose to purify this stimulatory activity and to obtain sequence information using mass spectrometry and conventional microsequencing methods for peptides. This technique might provide a more general approach for the identification of antigens recognized by gammadelta T cells. 3. To study the response of normal Vdelta6.3+gammadelta T cells to HSP-60 derived peptide antigens in vitro and in vivo. Taking advantage of a new Vdelta6.3 specific monoclonal antibody (mAb) and a strong correlation between the surface expression of Vdelta6.3 and reactivity with HSP-60, we will study possible effects of the presence of antigen on these cells in vitro and in vivo. This study addresses the question of whether normal gammadelta cells can respond to, and be tolerized by, soluble peptide antigen. 4. To develop an assay system for gammadelta T cell function using partially reconstituted severe combined immunodeficiency (scid) mice. Taking advantage of the observation that different stem cell sources vary in their potential to reconstitute gammadelta T cell populations, and the availability of large numbers of relatively homogeneous gammadelta T cells in gammadelta TCR transgenic mice, we will undertake to generate mice with defined gammadelta reconstitution patterns and then attempt to study immune responses of gammadelta T cell subsets and the possible effect of the presence of gammadelta T cells on alphabeta T cell and B cell responses.