Characterization of the E-selectin ligand on NK cells.

Abstract In this study we demonstrate that human CD56+CD16+/CD3- NK cells adhere to the E-selectin expressed by stimulated HUVEC in a sialidase- and Ca(2+)-dependent manner, and express a silylated Lex adhesion structure. We have characterized this sLe(x) epitope on NK cell in detail and show here that the sLe(x) on NK cells was not recognized by the CSLEX1 Ab, but was readily identified by two anti-di-sLe(x) Abs, KM-93 and FH-6. Furthermore, cleaving sialic acid with a sialidase treatment revealed a pool of Le(x) epitopes on the NK cells surface, providing further proof that NK cells express sLe(x) epitopes. Extensive protease treatments did not cleave the sLe(x) epitope from NK cells, which suggests that it could be linked to a lipid backbone. This di-sLe(x) was able to mediate adhesion to E-selectin, suggesting that it represents an essential part or is closely related to a selectin ligand on NK cells. We were also able to show that NK cells possess several alpha 2,3 sialyltransferases and alpha 1,3 or alpha 1,3/4 fucosyltransferases. These enzymes are crucial in the synthesis of sLe(x) epitopes on cell surfaces. Taken together, we provide evidence that NK cells have a di-sLe(x) oligosaccharide capable of adhesion to E-selectin, and NK cells have the machinery (i.e., relevant transferases) to generate these sialylated Lewis oligosaccharides.</jats:p

Down-regulation of monocytic VLA-4 leads to a decreased adhesion to VCAM-1

AbstractThe α4β1 integrin VLA-4 is expressed on practically all leukocytes, except on mature granulocytes. Here we show that in vitro treatment of monocytic cells with phorbol-12-myristate-13-acetate (PMA) leads to a selective decrease in the VLA-4 α-chain expression, both at the RNA and protein level. Meanwhile the expression of β1 and that of α5 another α-chain associating with β1 was seen to increase. The decrease of α4 expression was restricted to monocytic cells, and was not observed on other VLA-4-positive cells tested (MOLT-4 T cells and HOS sarcoma cells). The down-regulation of the VLA-4 α-chain was followed by a decreased binding capacity of the cells to recombinant VCAM-1. This data indicates that while previous findings show that the integrin-dependent adhesion may rapidly be regulated by altering the avidity of the interacting molecules, their quantitative modulation also has a clear impact on adhesion

Ventilation Onset Prior to Umbilical Cord Clamping (Physiological-Based Cord Clamping) Improves Systemic and Cerebral Oxygenation in Preterm Lambs

Developmen