Interleukin 1 in the in vitro antigen-induced antibody response in the human adult and newborn.

Previous studies have shown that in vitro stimulation of human B lymphocytes with antigens such as ovalbumin (OA) induces the formation of small antigen-specific plaque-forming cells (PFC) but precludes the activation of the B cells into full-blown antibody-secreting cells. Insufficient production of T cell-derived growth and differentiation factors appears to be the basis of the phenomenon. Furthermore, cord blood B lymphocytes required 100 times less OA to become activated in vitro into antigen-specific PFC, and the distinct antigen-handling capacities of neonatal monocytes are the basis of this result. We have studied the role of interleukin 1 (IL-1) in the in vitro response of B lymphocytes from either cord blood or adult blood to OA. Addition of IL-1 to the B-cell cultures significantly increased the number of PFC, and about 50% of the plaques now appeared to be high-rate IgM anti-OA-secreting PFC. The IL-1-mediated increase in the PFC response was shown to be based on potentiation of T-helper cell activity. The differences between cord blood and adult blood mononuclear cells in the optimal OA concentration required for effective in vitro activation of B cells remained the same upon addition of IL-1. This result shows that the phenomenon is independent of IL-1.