Differential expression of homing receptors and vascular addressins in tonsils and draining lymph nodes:: Effect of Brucella infection in sheep

The differential expression of homing receptors (HR) and complementary vascular addressins was studied in T and B lymphocytes from ovine tonsils and draining lymph nodes (LN) in uninfected and Brucella melitensis-infected sheep. In uninfected sheep, CD4(+)CD25(+) T cells expressed proportionally more L-selectin and beta 1 integrin than beta 7 integrin in pharyngeal and palatine tonsils and in parotid LN (PLN), retropharyngeal LN (RLN) and the peripheral prescapular LN (PSLN). In contrast, memory CD4(+)CD45RA(-) T cells expressed an equivalent proportion of the three HR in PLN and PSLN, whereas beta 1 and beta 7 integrins were proportionally more expressed than L-selectin in pharyngeal tonsil. 07 integrin was proportionally more expressed than beta 1 integrin or L-selectin in palatine tonsils, RLN and the mucosal mesenteric LN (MLN). beta 1 integrin was proportionally more expressed in IgG(+) and IgA(+) cells than beta 7 integrin and L-selectin in tonsils, PLN and RLN. The main endothelial addressin expressed on venules in both pharyngeal and palatine tonsils, the PLN and RLN, as well as in the PSLN, was the peripheral PNAd, while in the MLN it was MAdCAM-1. Conjunctival infection by Brucella resulted in an increase of CD4(+)CD25(+) and CD4(+)CD45RA(-) T cell subsets, which was associated to modifications of HR expression. CD4(+)CD45RA(-) T cells expressed proportionally more beta 1 and beta 7 integrins than L-selectin in regional PLN and RLN, but also in PSLN. The infection induced an increase of IgG(+) and IgA(+) cell percentages expressing beta 1 integrin in all LN, and also beta 7 integrin in the RLN. PNAd continued to be expressed on venules of tonsils and draining LN after Brucella infection, and MAdCAM-1 was also weakly expressed on RLN venules. These results suggest that lymphocyte trafficking through tonsils and draining LN could involve L-selectin/PNAd interactions, as well as beta 1 or beta 7 integrin, possibly in interaction with VCAM-1 or MAdCAM-1. The homing of antigen-specific lymphocytes in these tissues could be modulated after conjunctival infection with Brucella, which induces the recruitment of lymphocytes that express both beta 1 and/or beta 7 integrin in regional and more distant LN. (c) 2006 Elsevier B.V. All rights reserved.