Differential expression of adhesion molecules and chemokines between nasal and small intestinal mucosae: Implications for T- and sIgA⁺ B-lymphocyte recruitment

Nasal and small intestinal mucosae are the first sites of contact with infectious agents and the sites of T-cell-mediated and secreted immunoglobulin A (IgA)-mediated defences against pathogens. We investigated the factors controlling the infiltration of CD3⁺ T lymphocytes and surface IgA⁺ (sIgA⁺) B lymphocytes into swine epithelium and lamina propria (LP) within and between these two mucosal effector sites. Vascular addressins, vascular cell adhesion molecule 1 and mucosal addressin cell adhesion molecule-1 were reciprocally expressed in both mucosae. Strong expression of α₄β₁ relative to α₄β₇ was characteristic of CD3⁺ T cells in nasal mucosa LP and epithelium and of sIgA⁺ cells in nasal mucosa epithelium. The same profile was observed on corresponding blood cells. Conversely, higher levels of integrins β₇ and α₄β₇ than α₄β₁ were characteristic of CD3⁺ T cells and sIgA⁺ cells in the small intestine. However, about 40% of the LP-activated sIgA⁺ cells displayed sIgA^high, integrin α₄ and integrin α₄ expression. Whereas CCL19, CXCL12, CCL21 and CCL28 messenger RNAs were similarly expressed in both mucosae, CCL25 messenger RNA was only expressed in the small intestine. Thus, the nasal and small intestine mucosae represent separate compartments for infiltration by CD3⁺ T cells and sIgA⁺ effector cells, with the exception of a population of small intestine activated sIgA⁺ cells, which may gain access to both mucosae.