Intestinal exposure to a parasite antigen in utero depresses cellular and cytokine responses of the mucosal immune system

The response of the mucosal immune system of 4-6-week old lambs to viable Trichostrongylus colubriformis larvae was compared in two groups of animals, one exposed to T. colubriformis antigen and the other to saline while in utero. Exposure to larval antigen two-thirds of the way through gestation resulted in significant reduction in the frequency of jejunal goblet cells and of ileal eosinophils, CD1b⁺ antigen-presenting cells and CD4⁺, CD5⁺ and CD8⁺ cells. However, it resulted in a significant increase in the jejunal CD8⁺ response to postnatal challenge. The expression of the cytokines TNF-α and IL-1β in the ileum, and of jejunal NSE, was significantly reduced by in utero exposure, whereas those of jejunal TNF-α and ileal TGF-β were increased. The observed changes in cellular and cytokine responses to challenge with viable larvae, in those lambs previously exposed in utero, indicated that the intestinal mucosal immune system remains susceptible to down-regulation until considerably later in foetal development than is the case for other components of the immune system.