THE PEYER PATCH HIGH ENDOTHELIAL RECEPTOR FOR LYMPHOCYTES, THE MUCOSAL VASCULAR ADDRESSIN, IS INDUCED ON A MURINE ENDOTHELIAL-CELL LINE BY TUMOR-NECROSIS-FACTOR-ALPHA AND IL-1

The specificity of lymphocyte homing from the blood into a tissue is d etermined in part by complementary pairs of adhesion receptors on lymp hocytes and endothelial cells termed homing receptors and vascular add ressins, respectively. The mucosal vascular addressin involved in lymp hocyte homing to Peyer's patches is a 66-kDa glycoprotein, MAdCAM-1. I nvestigation of the regulation and molecular genetics of MAdCAM-1 have been hampered by the lack of a murine cell line expressing this adhes ion molecule. We show herein using indirect immunofluorescence studies that MAdCAM-1 can be induced on a murine endothelial cell line, bEnd. 3, by cytokines and LPS. Western blot analysis of MAdCAM-1 purified by affinity column chromatography from TNF-alpha-treated bEnd.3 cells de monstrates a 66-kDa protein that comigrates in SDS-PAGE with the MAdCA M-1 constitutively found on high endothelial venules in murine mesente ric lymph nodes. Comparison of MAdCAM-1 expression on the bEnd.3 cells was made to the expression of adhesion molecules ICAM-1 and VCAM-1. M AdCAM-1 and VCAM-1 are not constitutively expressed on the bEND.3 surf ace but can be induced in a concentration-dependent manner by LPS, TNF -alpha, and IL-1.ICAM-1 is constitutively expressed on the endotheliom a surface and expression is increased by TNF-alpha, IL-1, LPS, and IFN -gamma. Surface expression of MAdCAM-1 peaks 12 to 18 h after exposure to TNF-alpha and remains elevated at 48 h, whereas expression of VCAM -1 peaks at 4 h and inducible ICAM-1 peaks between 4 and 18 h. Interes tingly, IFN-gamma has differential effects on expression of these thre e adhesion receptors. IFN-gamma alone induces VCAM-1 and enhances ICAM -1 expression, but does not induce MAdCAM-1. Furthermore, although, pr eincubation of bEND.3 cells with IFN-gamma modestly increases the indu ction of ICAM-1 and VCAM-1 in response to TNF-alpha and IL-1, it drama tically reduces the TNF-alpha, IL-1, and LPS-induced expression of MAd CAM-1. MAdCAM-1 on bEnd.3 cells is functional as the murine T lymphoma TK1, known to bind MAdCAM-1, also binds to TNF-alpha-stimulated endot helioma but not to unstimulated cells. This binding is blocked by the antibodies against MAdCAM-1 and against the alpha4-chain of its integr in receptor, alpha4beta7, on TK1 cells. These data demonstrate that bE ND.3 cells can be induced to express functionally active MAdCAM-1 by i nflammatory cytokines and that MAdCAM-1 expression can be regulated, a t least in part, independently of ICAM-1 and VCAM-1 expression.