Characterization of Autonomic Nerve Markers and Lymphocyte Subsets in the Ileal Peyer’s Patch of Pigs Infected Experimentally with Brachyspira hyodysenteriae J. Kaleczyc * , P. Podlasz * , A. Winnicka † , W. Wasowicz * , W. Sienkiewicz * , J. Zmudzki ‡ and M. Lakomy * *Department of Animal Anatomy, Faculty of Veterinary Medicine, University of Warmia and Mazury, Oczapowskiego 13, 10-719 Olsztyn, † Division of Animal Pathophysiology, Department of Pathology and Veterinary Diagnostics, Faculty of Veterinary Medicine, Warsaw University of Life Sciences and ‡ National Veterinary Research Institute, Pulawy, Poland Summary The aim of the present study was to investigate potential interrelationships between immune and neural ele- ments of Peyer’s patches in normal pigs (n ¼ 8) and in pigs infected experimentally with Brachyspira hyodysenteriae and suffering from swine dysentery (n ¼ 8). Assessment of tissue concentration of neuropeptides by enzyme linked immunosorbent assay revealed increased levels of galanin (GAL) and substance P (SP) in samples from the infected animals. In contrast, concentrations of vasoactive intestinal polypeptide (VIP) and somatostatin (SOM) were similar in both groups. Immunohistochemistry demonstrated reactivity of nerve fi- bres with antibodies specific for dopamine b hydroxylase, vesicular acetylcholine transporter, SOM, GAL, VIP and SP in the interfollicular region and peripheral areas of the Peyer’s patch lymphoid follicles. In the dysen- teric pigs, the GAL-positive nerve fibres were more numerous and more intensely labelled than those in the normal animals. Flow cytometry revealed a decreased percentage of CD21 + lymphocytes and lymphocytes ex- pressing T-cell receptor (TCR)-g, with or without CD8 (TCR-g + CD8  and TCR-g + CD8 + ), in the dysen- teric pigs as compared with the normal animals. Percentages of other lymphocyte subsets (CD2 + , CD4 + , CD5 + , CD8 + , CD5  CD8 + ) were comparable between the groups. Immunohistochemical investigations gen- erally correlated with results obtained by flow cytometry related to lymphocyte subpopulations. Swine dysen- tery can therefore affect neuroimmunomodulatory processes in the ileal Peyer’s patch, in addition to the large intestine. GAL and SP may play a specific role in this neuroimmune cross-talk. Ó 2010 Elsevier Ltd. All rights reserved. Keywords: autonomic nerve markers; ileal Peyer’s patch; lymphocyte subsets; pig; swine dysentery Introduction There is a growing body of evidence suggesting the existence of functional interconnections between the immune and nervous systems, although the data available are frequently incomplete and not always focussed on their relevance for different physiological and pathological states (Mignini et al., 2003; Nance and Sanders, 2007). Primary (i.e. bone marrow and thymus) and secondary (i.e. spleen and lymph nodes) lymphoid organs are supplied with an efferent autonomic and afferent sensory innervation. Lymph nodes of various somatic and visceral regions are supplied with nerve fibres that have been shown by immunohistochemistry (IHC) to express noradrenaline, acetylcholine, neuropeptide Y (NPY), vasoactive intestinal polypeptide (VIP), calcitonin gene-related peptide (CGRP) and substance P (SP). These neurotransmitter substances can alter immune responses as immune cells may express specific receptors able to bind them. Alternatively, changes in immune function Correspondence to: J. Kaleczyc (e-mail: jerzy.kaleczyc@uwm.edu.pl). 0021-9975/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.jcpa.2010.04.003 J. Comp. Path. 2010, Vol. 143, 248e257 Available online at www.sciencedirect.com www.elsevier.com/locate/jcpa