Structure and biological function of human IgD: XV. Biological potential of IgD-bearing cells from cord blood, and normal human adults

Abstract

Specifically purified intact IgG anti-human δ or F(ab′) 2 anti-δ stimulated the in vitro incorporation of [ 3H]thymidine by cord blood and adult human peripheral blood lymphocytes. The magnitude of stimulation was unrelated to the increased frequency of IgD-bearing cells observed in cord blood over that seen in adult blood. Purified T cells lacked the capacity to undergo mitogenesis when incubated with anti-δ antibody. Of special interest was the lack of anti-δ enhancement of phytohemagglutinin (PHA) responsiveness of cord blood lymphocytes that is often observed when adult peripheral blood lymphocytes are treated with anti-δ, then PHA. This observation could be interpreted as indicating: (a) that the anti-δ-activated neonatal B cells, or their lymphokines, were preferentially activating a population of suppressor cells, which in turn prevented the PHA-augmentation usually seen with adult cells, (b) that the neonatal B cells do not possess the T cell-augmenting capacity or, (c) that the neonate lacks a subpopulation of T cells that can be acted upon by the B-cell or B-cell factors.