ANALYSIS OF THE DISTRIBUTION OF HUMAN CD38 AND OF ITS LIGAND CD31 IN NORMAL-TISSUES

Human CD38 is a 45 kD ectoenzyme endowed with ADP-ribosyl cyclase and hydrolase activities. The molecule plays a central role in lymphocyte activation, proliferation and selectin-type adhesion with endothelial cells (HEC). A HEC surface molecule displaying all the features of a C D38L has been identified by, means of a mAb (Moon-1), able to block CD 38-mediated adhesion processes. The 130 kD molecule recognized by Moon -1 is CD31, a member of the Ig superfamily This paper reports on the a nalysis of the surface expression of CD38 and CD38L in various human t issues of adult origin and compared in some instances to the fetal (9- 14 weeks) counterparts. This was achieved by means of immunohistochemi cal techniques and analysis of purified cell populations. Among the sp ecimens analyzed, CD38 is expressed by a vast array of cells of lympha tic origin as well as by the skeletal and cardiac muscle fibers, the b ronchi (epithelial cells), the parotid gland (ductal epithelial cells) and hepatic sinusoids. On the contrary, CD31 proved constantly expres sed by HEC at high levels, independent of the oi gan ol tissue analyze d or of the kind of vessel. Other cells expressing CD38L were found in the lymphoid compartment (follicle mantle B cells and plasma cells), in the lungs (alveolar driers, alveoli and lymphatic vessels) and in t he kidney (glomerular cells). Interestingly, no fetal organ or tissue ever expressed CD38 and its ligand. The above results were enriched by the analysis of the expression of the five molecules on purified popu lations including mononuclear cells from the lamina propria of the gas tro-intestinal tract and broncho-alveolar lavage lymphocytes.