The role of two distinct endothelial molecules, vascular adhesion protein-1 and peripheral lymph node addressin, in the binding of lymphocyte subsets to human lymph nodes |
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Authors: | M Salmi J Hellman S Jalkanen |
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Affiliation: | MediCity Research Laboratory, University of Turku, Finland. marko.salmi@utu.fi |
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Abstract: | Lymphocyte binding to high endothelial venules (HEV) in noninflamed peripheral lymph nodes (PLN) relies heavily on two endothelial adhesion molecules called vascular adhesion protein-1 (VAP-1) defined by mAb 1B2 and the peripheral lymph node addressins (PNAd) defined by mAb MECA-79. Data from several different groups indicate that these two molecules share several characteristics in expression, biochemical structure, and function, raising the possibility that VAP-1 may be identical to the 170- and 90-kDa species of PNAd glycoproteins. In this study, we show that many PLN HEV coexpress these two molecules. In parallel SDS-PAGE analyses, the m.w. of the 90- and 170-kDa forms of these molecules are indistinguishable. Nevertheless, we show by different metabolic labelings, by reciprocal cross-precipitations, and by immunofluorescence stainings of newly established VAP-1 transfectants that the 90- and 170-kDa species of PNAd and VAP-1 are distinct molecules. In functional terms, VAP-1 is strikingly selective in mediating PLN HEV adhesion of CD8-positive, but not of CD4-positive T cells. In contrast, PNAd contributes to the adhesion of both CD4-positive and CD8-positive cells to these vessels. Together, these data show that initial adhesion of CD8-positive lymphocytes to PLN HEV requires a PNAd- and a VAP-1-dependent step that are both essential and may occur simultaneously or sequentially. |
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