Characterization of human umbilical cord blood lymphocyte subsets fractionated on immobilized peanut agglutinin.

Human cord blood mononuclear cells from single donors were separated on minicolumns of peanut agglutinin (PNA) coupled to Sepharose beads to yield two fractions: unbound cells (PNA-, 78%) that were eluted with phosphate buffered saline, and bound cells (PNA+, 22%) eluted with 0.2 M D-galactose. The total yield was 86% and the cells were fully viable. There was no enrichment for macrophages or for surface immunoglobulin positive (B) cells in either the PNA+ or PNA- subset. Only 26% of the PNA+ lymphocytes formed rosettes with sheep red blood cells, in contrast to 53% of the PNA- lymphocytes. The response of the PNA+ cells to mitogens and allogeneic stimulation was considerably lower than that of the PNA- cells, while that of the latter was higher than the response of the unseparated cells. The average ratios of response of the PNA+ to PNA- cells were 0.25 for PHA, 0.20 for concanavalin A, 0.15 for pokeweed mitogen, and 0.15 In the mixed lymphocyte reaction. when tested with monoclonal antibodies to lymphocyte surface markers, it was found that the PNA+ fraction was depleted of mature T cells and enriched in Ia positive cells. Our data show that the low reactivity of human cord blood mononuclear cells may be ascribed to the presence of a subpopulation of lymphocytes which are immunologically immature. They also provide further evidence that in humans the PNA receptor is a marker for immature T or B lymphocytes.