PERIPHERAL-TYPE BENZODIAZEPINE RECEPTORS AND DIAZEPAM BINDING INHIBITOR-LIKE IMMUNOREACTIVITY DISTRIBUTION IN HUMAN PERIPHERAL-BLOOD MONONUCLEAR-CELLS

Peripheral-type benzodiazepine receptors (pBZr) in human lymphocytes h ave been detected only in mixtures of peripheral blood mononuclear cel ls (PBMC). The present investigation was designed to describe precisel y the location of pBZr in the various sets and subsets of PBMC, purifi ed using monoclonal antibodies to specific PBMC surface markers. Site densities and affinities of pBZr were measured in the intact cells by conventional binding, using H-3-PK 11195 as a ligand. Moreover, we use d a specific radioimmunoassay to identify in these cells the presence of the polypeptide diazepam binding inhibitor (DBI), a putative endoge nous ligand for various benzodiazepine receptors including the periphe ral type. Two major findings are derived from these studies: first, th e coexistence of pBZr and DBI, or closely related immunoreactive mater ial, in all major lymphocyte sets and subsets, as well as in monocytes . And second, the significant correlation (r = 0.87, p < 0.001) observ ed between the density of pBZr in a given cell type and its abundance of DBI like-immunoreactivity (DBI-LI). For both pBZr and DBI-LI conten t the cell distribution was monocytes > B cells and large granular lym phocytes > T cells (CD3+ set or CD4+ and CD8+ subsets) (ANOVA: pBZr: F = 114.11, p < 0.001; DBI-LI: F = 20.79, p < 0.001). The results are d iscussed in terms of the possibility that DBI and pBZr might share a r elevant interaction in immunocompetent elements, thereby contributing to a new route of connection between the immune and the nervous system s.