Catecholaminergic, cholinergic and peptidergic innervation of gut-associated lymphoid tissue in porcine jejunum and ileum

With its abundance of neurons and immunocytes, the gut is a potentially imp ortant site for the study of the interaction between the nervous and immune systems. Using immunohistochemical techniques, we tested the hypothesis th at gut-associated lymphoid tissue in the porcine small intestine might rece ive catecholaminergic, cholinergic and peptidergic innervation. Antibodies against protein gene product (PGP) 9.5 were employed to detect neuronal mem branes; antibodies against tyrosine hydroxylase (TH), type 2 vesicular mono amine transporter (VMAT-2) and choline acetyltransferase (ChAT) were used t o detect catecholaminergic and cholinergic neurons; and antibodies to neuro medin U-8 (NMU-8), substance P (SP) and vasoactive intestinal peptide (VIP) were also used. PGP9.5-immunoreactive nerve fibers were observed between j ejunal Peyer's patch (PP) follicles and in submucosal ganglia localized at the base of continuous ileal PP. Many ChAT-positive and a few TH-/VMAT-2-im munoreactive neurons or axons adjacent to jejunal and ileal PP were observe d. Neurons and fibers from ganglia situated between or at the base of PP fo llicles manifested robust immunoreactivities to VIP and NMU-8; relatively l ess SP immunoreactivity was observed at these locations. All neuromedin-U 8 -positive neurons observed exhibited immunoreactivity to ChAT as did some V IP-positive neurons. The specific chemical coding of enteric neurons in clo se apposition to jejunal and ileal PP and the differential localization of neuropeptides within the jejunal and ileal PP are indicative of neuroimmuno modulation at these sites.