Expression of GlyCAM-1, an endothelial ligand for L-selectin, is affected by afferent lymphatic flow

The interaction of naive, L-selectin-bearing lymphocytes with counterreceptors on the surface of high endothelial venules (HEV) is the initial step in the extravasation of these cells from the bloodstream into the peripheral lymph node. Recently, two sulfated glycoprotein ligands, 50 and 90 kDa, respectively, have been identified as ligands for L-selectin using an L-selectin-IgG chimera. cDNA cloning of one of these molecules, the 50-kDa sulfated glycoprotein (glycosylation-dependent cell adhesion molecule 1 [GlyCAM-1]), has shown it to be a mucinlike scaffold that presents a carbohydrate ligand(s) to the lectin domain of L-selectin. Herein, we analyze the factors that might regulate the expression of these ligands. Ligation of afferent lymphatics results in a complete loss of the mRNA for GlyCAM-1. In addition, L-selectin-mediated adhesion, as inferred by binding of an L-selectin-IgG chimera, is also lost on interruption of afferent flow. It thus appears that a soluble and/or cellular component(s) of afferent lymph regulates the expression of GlyCAM-1 mRNA and the resultant HEV adhesiveness for lymphocytes

Selective modulation of the expression of L-selectin ligands by an immune response

BACKGROUND: The adhesion molecule L-selectin is expressed on the cell surface of lymphocytes and mediates their migration from the bloodstream into lymph nodes. L-selectin is able to recognize four glycoprotein ligands, three of which--Sgp50, Sgp90, and Sgp200--are sulphated, bind specifically to L-selectin and are synthesized by the high endothelial venules of the peripheral and mesenteric lymph nodes. One of these three sulphated L-selectin ligands, Sgp90, has been shown to be identical to the known surface marker CD34 and is expressed on the cell surface of endothelial cells. The cDNA encoding Sgp50 has been cloned, and its product, which has been designated GlyCAM-1, is secreted. The third ligand, Sgp200, is both secreted and cell-associated. We have investigated how the expression of these sulphated glycoproteins is regulated during an immune response. RESULTS: Here we demonstrated that, during a primary immune response, the expression and secretion of both GlyCAM-1 and Sgp200 are reduced, recovering to normal levels 7-10 days after antigen stimulation. In contrast, the expression of cell-associated CD34 and Sgp200 is relatively unaffected. These results may account for the modest decreases in the binding of an L-selectin-IgG fusion protein to high endothelial venules of inflamed peripheral lymph nodes that have been observed after antigen exposure. In vivo experiments show that, following the decrease in the levels of secreted GlyCAM-1 and Sgp200, migration of lymphocytes from the blood stream into lymph nodes remains L-selectin-dependent, but more lymphocytes home to antigen-primed than unprimed peripheral lymph nodes. CONCLUSIONS: We suggest that the secreted forms of the L-selectin ligands GlyCAM-1 and Sgp200 act as modulators of cell adhesion, and that cell-associated CD34 and Sgp200 are the ligands that mediate the initial loose binding of lymphocytes to high endothelial venules

Design of 2‐hydroxyethyl methacrylate‐functional macromonomer dispersants by semi‐batch cobalt chain transfer polymerization

Acrylic resins for automotive coatings are produced in nonaqueous dispersions (NAD) of nanometer size. These must be sterically stabilized by oligomeric dispersants, which are complex reactive oligomers possessing vinyl and hydroxyl functionalities, controlling the size of the nanocolloid. Hence, we have developed a kinetic Monte Carlo (kMC) model to improve the molecular structure of 2-hydroxyethyl methacrylate-functionalized poly (butyl methacrylate) (pBMA) dispersants of ca. 6,000 g/mol produced via semi-batch cobalt chain transfer polymerization (CCTP). The kMC-predicted degree of functionalization is benchmarked against a novel analytic expression suitable for oligomers. Stepwise adjustment of the semi-batch feed program illustrates the successive improvement in molecular structure of the dispersant product, finally arriving at a functionalization degree close to the theoretical maximum for CCTP