Evidence for the existence of IL-4 and IFN gamma secreting cells in the T cell repertoire of naive mice

Modulation of IL-4 production in murine spleen cells by prostaglandins

Recently, it has been reported that IL-4 production by murine Th2 cell lines is insensitive to inhibition by E-type prostaglandins. In the present study, IL-4 production in vitro by freshly isolated concanavalin A (Con A)-stimulated murine spleen cells was readily suppressed by PGE2 with an I50 of 2 nM. Comparable suppression by PGE2 was seen after priming by anti-CD3 epsilon antibody instead of Con A or with other changes in the culture conditions. PGE2 was an effective inhibitor after elimination of Ly2.2+ T cells, consistent with a direct effect on Th2 cells. In the absence of added prostaglandins, IL-4 production was enhanced 1.5- to 7.0-fold by 0.2-2.0 microM indomethacin, indicating that endogenous arachidonate metabolites such as PGE2 and PGI2 regulate IL-4 production in our usual culture system. The inhibition of Th2 cell secretion by PGE2 in vitro may have physiologic and pharmacologic implications for the regulation of Th2 cell function and IgE production in vivo.

Allergen-dependent induction of interleukin-4 synthesis in vivo

The ability of freshly derived T cells to produce interleukin-4 (IL-4) remains controversial. Many groups report that freshly derived antigen-, allogen- or mitogen-activated CD4 T cells produce almost exclusively IL-2, acquiring the capacity to produce a spectrum of cytokines following culture, rest and restimulation. In contrast, it is demonstrated here that in vivo exposure to protein allergens induces rapid, co-ordinate activation of IL-4 and interferon-gamma (IFN-gamma) gene expression. Overnight culture of spleen cells obtained from mice immunized with ovalbumin (OVA) or ragweed extract (RAG) in alum adjuvant elicits strong IL-2 and IL-4 responses within 14 hr of culture. T cells from mice immunized with allergen in complete Freund's adjuvant (CFA) generate strong IL-2 and IFN-gamma production, but virtually no IL-4, while unimmunized mice do not respond detectably to allergen in vitro (< 1 U). Unlike the differential pattern of cytokine synthesis observed following antigen-specific in vitro restimulation, cultures derived from naive and allergen-primed animals yield virtually equivalent IL-4, IL-2 and IFN-gamma synthesis upon polyclonal restimulation with anti-CD3 mAb 145-2C11 or concanavalin A (Con A), a finding which underlines the importance of the experimental conditions selected for in vitro analysis of in vivo cytokine gene expression. Collectively, the results indicate that the mode of immunization is critical to the pattern of cytokine response elicited and consequently to the type of antibody response which develops.(ABSTRACT TRUNCATED AT 250 WORDS)