Induction of T-lymphocyte adhesion by histidine-proline-rich glycoprotein and concanavalin A

Histidine-proline-rich glycoprotein (HPRG) is a plasma protein which binds to a specific receptor on T-lymphocytes and represses T-cell activation and proliferation. In the presence of Concanavalin A (Con A), HPRG causes human T-lymphoblastic MOLT-3 cells and a fraction of normal human peripheral blood lymphocytes to attach to the culture dish and significantly change morphology by either extending processes or becoming elongated at the poles, respectively. HPRG and Con A are just as effective at inducing MOLT-3 attachment in a soluble or an immobilized form. MOLT-3 cell attachment is specific for HPRG, dose-dependent, and reversible in 72 hr. Only certain T-cell mitogenic lectins, Con A and phytohemagglutinin, are effective at stimulating adherence. Mannose, glucose, fucose, and N-acetylglucosamine inhibit HPRG-induced MOLT-3 cell attachment to different degrees, with methyl alpha-D-mannopyranoside being the most potent inhibitor. We propose that in vivo HPRG together with a naturally expressed lectin induces T-lymphocyte adhesion to initiate cell migration to sites of inflammation.