Expression and immunohistochemical localization of the neonatal Fc receptor (FcRn) in the mammary glands of the Egyptian water buffalo

Abstract

Although a marginal placental transfer of maternal immunoglobulin (Ig) has been demonstrated in buffalo, the colostrum still provides the main source of immune components and nutrients to neonate buffalo calves. The neonatal Fc receptor (FcRn) transports maternal Ig across the gut wall and is involved in the transport of IgG in the mammary gland. In this study we used RT-PCR to examine the gene expression of FcRn in the mammary gland during several physiological states of the Egyptian water buffalo. The buffalo FcRn showed a high sequence homology to that of other mammalian species and especially the cow. Immunohistochemistry demonstrated positive immunolabelling of FcRn in the epithelial cells of the acini and ducts of the examined mammary gland tissue. Remarkable differences in both the cellular localization and in the intensity of FcRn immunopositivity were observed depending on the functional state of the mammary gland tissues. In late pregnancy, the FcRn immunolabelling was homogeneously distributed in the cytoplasm of the epithelial cells. In recently parturient animals, positive FcRn immunolabelling was mainly located at the luminal surface and apical cytoplasm of the mammary gland epithelium, while in dry and lactating animals, the FcRn immunolabelling was in the apical cytoplasm of the cells. The strongest FcRn immunolabelling was observed in late pregnancy and in recently parturient animals. In conclusion, the present data support the notion that FcRn might be involved in the transfer of maternal immunoglobulins and in the local defense mechanism of the mammary gland.