Anti-Mouse MAdCAM-1 (MECA-89) - Purified <i>in vivo</i> PLATINUM^TM Functional Grade (M1421-GRP)

MAdCAM-1 is a cell adhesion leukocyte receptor expressed by mucosal venules that helps direct lymphocyte traffic into mucosal tissues and regulates the passage and retention of leukocytes1, 2. MAdCAM-1 binds integrin receptor α4β7 and L-selectin2, 3, 4. Two alternatively spliced isoforms of MAdCAM-1 exist5, both of which are capable of binding α4β72. MECA-89 was generated by immunizing Wistar rats with endothelial cells isolated from BALB/c mesenteric and peripheral lymph nodes 6. Immunohistological screening of hybridomas yielded two mAbs, MECA-367 and MECA-89, that stain high endothelial venules (HEVs) in mucosal lymphoid organs and Peyer’s patches, but not peripheral lymph nodes (axillary, brachial, popliteal, and inguinal). Immunofluorescence staining of high endothelial cells shows that both MECA-367 and MECA-89 react with antigens on the cell surface. The epitopes for MECA-367 and MECA-89 are distinct. MECA-367 recognizes the N-terminal immunoglobulin domain of MAdCAM-l, and MECA-89 recognizes the second immunoglobulin domain 4,5. MECA-89 reacts with the same vessels as MECA-367 and binds to isolated MECA-367 antigen; however, unlike MECA-367 it has no effect on lymphocyte binding 6. Additionally, MECA-89 has no effect on MAdCAM-1 binding to α4β7 in vitro 7, but L-selectin dependent adhesion is lost in the presence of MECA-89 4. Additionally, MECA-89 has no significant effect on activated cells, but all interactions are inhibited following subsequent injection of anti-α4 Fab fragments 4. In vivo, MECA-89 inhibits L-selectin-dependent rolling but not direct α4β7-dependent attachment of Mn2+ activated lymphocytes.