Expression of adhesion molecules in the rectum‐associated lymph nodules of pre‐ and postnatal specific pathogen‐free rats

BACKGROUND AND AIM: The developmental process of lymphoid tissues in the gastrointestinal tract is still unclear. The aim of the present study was to explore the expression of adhesion molecule in rectum-associated lymph nodules (RALN) of specific pathogen-free (SPF) rats at fetal and early postnatal periods of development. METHODS: Immunohistochemical analysis was carried out of select adhesion molecules and lymphocyte subsets in lymph nodules of the rat rectal region. RESULTS: Mucosal addressin cell adhesion molecule (MAdCAM)-1 expression was detected in the colonic mucosa on day 16 of gestation. Expression was strong in endothelial cells of all blood vessels in the entire colonic mucosa until day 7 after birth. On day 10 after birth, MAdCAM-1 was strongly expressed and confined to the high endothelial venule (HEV) in the submucosa of RALN, and was rarely detected in the blood vessels other than the HEV. In contrast, intercellular adhesion molecule (ICAM)-1 expression was absent in fetal colonic mucosa but appeared just after birth. Only a very small number of lymphocyte-function associated antigen (LFA)-1-positive cells appeared in the mucosa on day 16 of gestation but by day 19 of gestation a large number of these cells had rapidly aggregated in the mucosa of the ante-mesenteric side of the developing colon. These cells also expressed interleukin-7 receptor (IL-7R), and some were positive for CD4 and Mar-1 markers. CONCLUSION: The region of RALN undergoes rapid and dynamic changes in adhesion molecule expression during gestation, which may regulate interactions with intestine-associated immune cells shortly after birth.