IL-1 secretion and membrane IL-1 expression by neonatal spleen cells during soluble antigen presentation

Antigen presentation and IL-1 production by neonatal spleen cells were studied in a murine model. The T-helper-cell line (D10-G4.1) (D10), which is specific for soluble antigen presented on syngeneic antigen-presenting cells and dependent on IL-1 for its proliferation, was used as an indicator cell for the ability of syngeneic neonatal or adult spleen cells to present antigen and produce IL-1. The antigen-presenting capacity of neonatal spleen cells is low as attested by D10 proliferation. During antigen presentation there is an augmentation of IL-1 production by the antigen-presenting spleen cell population. However, neonatal spleen cells do not respond to the same levels as do adult spleen cells. These reduced levels of secreted IL-1 cannot be attributed to a low potential for producing IL-1 as attested by the high levels of IL-1 made by these cells after induction by a crude IL-1 inducer factor (IL-1-IF) and by the stimulus of the IL-1-IF produced by D10 cells during antigen presentation by paraformaldehyde-fixed adult cells. The spontaneous expression of membrane IL-1 by neonatal cells is low. Membrane IL-1 levels on neonatal cells can be brought to adult levels by induction with IL-1-IF. Neonatal spleen cells have an impaired capacity to process and/or present soluble antigen. This impairment leads to a decreased stimulus of the T helper cell to produce inducer factors and thus a reduced level of IL-1 production by the neonatal cells during antigen presentation.