Induction of interleukin-4 production in neonatal IgE+ cells after crosslinking of maternal IgE.

Transfer of maternal IgE antibodies to the neonate with the colostrum has been described in different mammalian species. Previous work in horses has shown that IgE bound to the surface of neonatal basophils is solely of maternal origin. However, the functional role of the maternal IgE transfer remained unclear. We hypothesized that maternal IgE mediates the onset of innate IL-4 production in equine neonatal basophils. Intracellular IL-4 production was measured in PBMC of newborn and older foals by flow cytometric analysis. A small population of IL-4(+) cells was observed in the peripheral blood at days 3-5 after birth. Phenotyping of the IL-4(+) cells showed that they were IgE(+)/MHCII(low)/CD4(-) cells. Magnetic cells sorting of the IgE(+)/MHCII(low) cells identified them as basophils. Anti-IgE stimulation in vitro induced IL-4 in IgE(+)/MHCII(low) basophils, but not in MHCII(+) cells or cells collected before colostrum ingestion. In conclusion, stimulation via maternal IgE antibodies mediated innate IL-4 production in neonatal basophils which might provide a paragenetic mechanism to promote the development of adaptive T-cell responses in the neonate after birth.