The Experimental Immunology Branch flow cytometry laboratory currently supports 60 individual research projects for 45 investigators. These investigations involve quantitative single cell analysis of parameters associated with cell types freshly prepared from different species/tissues, as well as spectrum of in vitro cultured cells. Basic research support is provided to members of the EIB and the Immunology Branch, as well as to other members of DCBD. Currently supported projects include a broad range of applications in the areas of cellular immunology, immunochemistry, transplantation biology, clinical immunology, immunogenetics, tumor immunology, and molecular immunology. These include, but are not limited to, the following studies: a) in vivo and in vitro analyses of intra-cellular signalling via T cell surface molecules, b) characterization of T cells from animals with genetic or induced immune dysfunction; c) studies of the pathogenesis of graft-versus-host disease; d) analyses of the correlations between T cell memory and the quantitative expression of cell surface adhesion molecules; e) investigations of T cell ontogeny and differentiation; and f) analyses of the mechanisms involved in marrow graft rejection versus acceptance.