Analysis of human thymocyte subpopulations using discontinuous gradients of albumin: precursor lymphocytes in human thymus

Abstract

Abstract Precursor lymphocytes, obtained from human tissue on bovine serum albumin (BSA) gradients followed by removal of sheep erythrocyte (E)‐reactive thymocytes on Ficoll, are the predominant lymphoid subpopulation found in young fetal thymuses. This subpopulation shows a progressive decline in relative numbers during fetal life, accompanied by a rise in both the relative and absolute numbers of E‐reactive thymocytes. Precursor thymocytes differentiate in vitro to E‐reactive cells resembling T cells in their morphology, sedimentation on BSA gradients, and response to phytohemagglutinin. Agents tending to increase intracellular concentrations of cyclic‐AMP accelerate the rate of differentiation of precursor cells to lymphocytes which closely resembleT cells.