IMMUNOHISTOCHEMICAL LOCALIZATION OF PEPTIDERGIC NERVE-FIBERS AND NEUROPEPTIDE RECEPTORS IN PEYERS-PATCHES OF THE CAT ILEUM

This study examined the distribution of peptidergic nerve fibers in Pe yer's patches to determine whether appropriate receptors were present. Vasoactive intestinal peptide (VIP), substance P (SP), calcitonin gen e-related peptide (CGRP) and receptors for VIP and SP were localized i n lymphoid follicles of the cat ileum using a combined indirect horser adish peroxidase and streptavidin-biotin method. The margins of follic les were innervated by nerve fibers containing VIP, SP and CGRP. Nerve fibers were predominantly around lymphatics and high endothelial venu les at the edges of follicles. Specific receptors for VIP and SP were present at the margins of follicles and in the lamina propria around c rypts. VIP receptors were numerous on T cells within and around high e ndothelial venules and lymphatic vessels and at the margins of follicl es. SP receptors were identified on a small number of T and B cells, g ranulocytes and macrophages, restricted to the margins of follicles. T he defined distribution in ileal lymphoid tissue of nerve fibers conta ining VIP and SP and the corresponding localization of their appropria te receptors support immunoregulatory roles for neuropeptides in mucos al immunity.