Downregulation of the goat beta-defensin-2 gene by IL-4 in caprine intestinal epithelial cells infected with Eimeria spp.

Defensins are antimicrobial peptides that are produced by leukocytes and epithelial cells. Recent advances indicate that these peptides play an important role in innate immune responses. Nonetheless, the role of defensins in caprine eimeriosis remains unknown. Therefore, this study investigated the expression of a goat beta-defensin, named GBD-2 in caprine intestinal epithelial cells (CIEC) stimulated with recombinant bovine interferon-gamma (IFN-gamma) in the presence or absence of recombinant bovine interleukin-4 (IL-4) by a reverse transcriptase-polymerase chain reaction (RT-PCR) assay. GBD-2 mRNA was clearly expressed in IFN-gamma-stimulated CIEC. On the other hand, the direct addition of IL-4 showed no significant effect on GBD-2 expression in CIEC. However, when supernatants from peripheral blood mononuclear cells (PBMC) cultured with IL-4 were added to CIEC, the expression of GBD-2 decreased. To elucidate if IFN-gamma functions as a signaling molecule that facilitates the generation of GBD-2 against Eimeria spp. in goats, anti- IL-4 was added to PBMC from Eimeria-infected goats and levels of IFN-gamma in culture supernatants were determined by an enzyme-linked immunosorbent assay test. Results showed that IFN-gamma secretion increased when anti-IL-4 was added to PBMC. It then appears safe to suggest that IL-4 may be a further factor in the pathogenesis of goat coccidiosis and its induction may be part of an evasion strategy of the parasite to avoid pro-inflammatory responses.