EXPRESSION OF THE MUCOSAL VASCULAR ADDRESSIN, MADCAM-1 - ON SINUS-LINING CELLS IN THE SPLEEN

The MAdCAM-1 adhesion molecule is involved in lymphocyte homing into m ucosal sites and is expressed on high endothelial venules of Peyer's p atches and mesenteric lymph nodes, In the spleen, where high endotheli al venules are absent, expression can be found on cells in the margina l zone between red and white pulp. By immunohistochemistry and electro n microscopy it was demonstrated that in the spleen cells expressing M AdCAM-1 belong to the population of sinus-lining cells and that the ex pression is restricted to the sinus-lining cells closest to the lympho id white pulp. Lymphocytes that migrate from the blood into this white pulp area will have to pass through the rim of cells expressing MAdCA M-1. A functional role for MAdCAM-1 or its lymphocyte ligand, the alph a 4 beta 7 integrin complex, was investigated by in vivo short-term ho ming experiments with anti-MAdCAM-1 and anti-alpha 4 beta 7 antibodies , but no direct role for this receptor-ligand interaction could be dem onstrated.