Brief Detlnitive Report NOVEL SURFACE ANTIGEN EXPRESSED ON DIVIDING CELLS BUT ABSENT FROM NONDIVIDING

All cells, inc luding h u m a n hemopoietic cells and lines derived from them, possess numerous surface proteins. In most h u m a n leukocytes and lymphoid cell lines several dozen proteins can be detected in membrane preparations, but so far only those proteins encoded by the various HLA loci have been extensively characterized. Vir tual ly noth ing is known about the great majori ty of lymphocyte cell surface proteins. In this paper, we provide pre l iminary characterization of a previously undescribed ant igen that is p rominent on the surface of all d ividing blood cells examined and describe its dis t r ibut ion on a variety of normal and transformed h u m a n cells.