Isolation on discontinuous gradients of bovine albumin of a subpopulation of human lymphocytes exhibiting precursor characteristics

Purified subpopulations of lymphocytes were obtained from discontinuous bovine serum albumin (BSA) gradients and by rosetting sheep erythrocytes (E) or EAC1-3. Cells from layers 1 to 3 of the BSA gradient which failed to rosette with E were highly reactive with EAC1-3 and with anti-human IgM. Demonstrating a high spontaneous rate of DNA synthesis and primitive morphology, these cells responded to pokeweed mitogen, concanavalin A and alloantigens, but not to phytohemagglutinin or soluble antigens. Constituting from 0.5% to 3.0% of all lymphocytes from each of the tissues studied, these lymphocytes appear to represent an earlier stage in human lymphocyte development distinct from both T and B cells.