Delayed in vitro immunoglobulin production by cord lymphocytes.

Pokeweed mitogen-induced immunoglobulin (Ig) production by cord lymphocytes was studied in vitro by Ig-secreting plaque-forming cell (Ig-PFC) assay. Although adult mononuclear cells generated all of IgM-, IgG-, and IgA-PFC, cord mononuclear cells generated only IgM-PFC when cultured for seven days. The number of cord IgM-PFC was 102 +/- 26/10(4) mononuclear cells, being about one fourth of that of adult IgM-PFC. When cultured for 14 days, cord mononuclear cells formed increased numbers of IgM-PFC in contrast to adult cells and yielded IgG-PFC as well, indicating delayed Ig production. Cord T cells were much less effective at helping adult B cells to differentiate into Ig-PFC as compared with adult T cells. Substitution of adult T cells for cord T cell markedly improved the response of cord B cells. The present study demonstrates Ig secretion by cord lymphocytes in response to pokeweed mitogen stimulation. The results further indicate that the delayed Ig production by cord lymphocytes is largely due to functional immaturity of the T cells.