T and IgA B Lymphocytes of the Pharyngeal and Palatine Tonsils: Differential Expression of Adhesion Molecules and Chemokines

Abstract

The pharyngeal (Ph) and palatine (Pa) tonsils, although located in different regions of the upper aero‐digestive tract (UADT), are thought to protect the respiratory tract similarly against infections by inducing and disseminating T and surface IgA⁺ (sIgA⁺) B cells. We investigated the factors controlling the migratory properties of T and sIgA⁺ B lymphocytes in the UADT of pigs by comparing the expression of vascular addressins, homing receptors and chemokine transcripts in Ph/Pa tonsils, Peyer's patches (PP) and their draining lymph nodes (LN). The vascular addressin PNAd was detected on high endothelial venules in both tonsils, whereas mucosal addressin cell adhesion molecule‐1, otherwise present in PP and mesenteric LN, was not detected. More importantly, the vascular cell adhesion molecule‐1 (VCAM‐1) addressin was present in Ph tonsil and LN but neither in Pa tonsil nor in PP vascular cells, whereas both T and sIgA⁺ B lymphocytes displayed similar levels of α4β1^high integrin, the ligand of VCAM‐1. Analysis of transcript levels for several lymphoid (CCL19, CXCL12 and CCL21) and epithelial chemokines also demonstrated opposite chemokine mRNA ratios for Ph tonsil (CCL28 > CCL25) and PP, with Pa tonsil expressing very low levels of CCL28. Collectively, these data indicate that the differential compartmentalization of sIgA⁺ lymphocytes between Pa and Ph tonsils may partly result from the differential expression of VCAM‐1 and CCL28. They also suggest that tonsillar addressins and epithelial chemokines, rather than the cells intravasating it, control the regionalization of sIgA⁺ lymphocytes in the UADT.