CHARACTERIZATION OF PROSOMES IN HUMAN LYMPHOCYTE SUBPOPULATIONS AND THEIR PRESENCE AS SURFACE-ANTIGENS

Prosomes, also called ''multicatalytic proteinase'' (MCP) or ''proteas omes,'' are a new type of ubiquitous RNP particle present in some arch eobacteria and in all eukaryotic cells tested from yeast to human. The y were discovered as subcomplexes of untranslated messenger-ribonucleo proteins (mRNP) and later found to have a MCP activity putatively invo lved in antigen processing. Being composed of variable sets of charact eristic proteins and associating small RNAs (pRNA), families of indivi dual ''mosaic'' prosome particles seem to characterize the differentia tion type and physiological state of individual cells and tissues. Her e, prosomes from human lymphocytes, isolated and characterized biochem ically and by Western blot analysis, were found to differ in their sub unit composition compared to other human prosomes. Surprisingly, proso mal antigens were discovered at the outer surface of blood cells monit ored by flow cytometry with monoclonal antibodies to individual prosom al proteins. It was observed that human T and B lymphocytes have varia ble and characteristic prosomal antigens at their surface according to their CD classification. Interestingly, the lymphocyte subpopulations most strongly labeled by the anti-p25K and anti-p27K mAbs were the NK and B cells. (C) 1997 Academic Press.