The R6-5-D6 monoclonal antibody reacts with human CD54 also known as Intercellular Adhesion Molecule-1 (ICAM-1), is a single-chain transmembrane glycoprotein with a polypeptide core of 55 kDa and a member of the Ig superfamily. CD54 is typically expressed on non-hematopoietic cells such as endothelial cells, thymic epithelial cells, and fibroblasts but can also be expressed on macrophages, T-lymphoblasts, germinal center B cells and dendritic cells. CD54 is a ligand for LFA-1, a receptor found on leukocytes. When activated, leukocytes bind to endothelial cells via CD54/LFA-1 and then transmigrate into tissues. Pro-inflammatory cytokines such as IL-1, TNF and IFNγ induce CD54 expression on endothelial cells and fibroblasts. The R6-5-D6 antibody has been reported to inhibit the interaction of CD54 with leukocytes, thereby decreasing leukocyte adhesion to the vascular endothelium and inflammatory tissue injury.

INVIVOMAB ANTI-HUMAN CD54 (ICAM-1) (CLONE: R6-5-D6)

Vestweber, D., et al. (2013). “Cortactin regulates the activity of small GTPases and ICAM-1 clustering in endothelium: Implications for the formation of docking structures.” Tissue Barriers 1(1): e23862. Pubmed

Cortactin is an actin-binding molecule that regulates various cellular processes requiring actin dynamics. We recently described cortactin-deficient mice and despite its pivotal role for actin remodeling in vitro, these mice are surprisingly healthy. Analyzing cortactin functions in endothelium under inflammatory conditions, we found that cortactin is required for endothelial barrier functions and leukocyte extravasation in vivo. Importantly, these effects were not regulated by defective actin dynamics but instead by a failure to activate the small GTPases Rap1 and RhoG in endothelial cells. Defective RhoG signaling led to reduced ICAM-1 clustering that supported the interaction with leukocytes. These clusters originally seen as rings surrounding adherent leukocytes actually represented in many cases ICAM-1 containing protrusions as they were described before as docking structures. Thus, cortactin is essential for the formation of endothelial docking structures as well as for leukocyte adhesion and extravasation.

Schnoor, M., et al. (2011). “Cortactin deficiency is associated with reduced neutrophil recruitment but increased vascular permeability in vivo.” J Exp Med 208(8): 1721-1735. PubMed

Neutrophil extravasation and the regulation of vascular permeability require dynamic actin rearrangements in the endothelium. In this study, we analyzed in vivo whether these processes require the function of the actin nucleation-promoting factor cortactin. Basal vascular permeability for high molecular weight substances was enhanced in cortactin-deficient mice. Despite this leakiness, neutrophil extravasation in the tumor necrosis factor-stimulated cremaster was inhibited by the loss of cortactin. The permeability defect was caused by reduced levels of activated Rap1 (Ras-related protein 1) in endothelial cells and could be rescued by activating Rap1 via the guanosine triphosphatase (GTPase) exchange factor EPAC (exchange protein directly activated by cAMP). The defect in neutrophil extravasation was caused by enhanced rolling velocity and reduced adhesion in postcapillary venules. Impaired rolling interactions were linked to contributions of beta(2)-integrin ligands, and firm adhesion was compromised by reduced ICAM-1 (intercellular adhesion molecule 1) clustering around neutrophils. A signaling process known to be critical for the formation of ICAM-1-enriched contact areas and for transendothelial migration, the ICAM-1-mediated activation of the GTPase RhoG was blocked in cortactin-deficient endothelial cells. Our results represent the first physiological evidence that cortactin is crucial for orchestrating the molecular events leading to proper endothelial barrier function and leukocyte recruitment in vivo.

Williams, K. M., et al. (2011). “Choice of resident costimulatory molecule can influence cell fate in human naive CD4+ T cell differentiation.” Cell Immunol 271(2): 418-427. PubMed

With antigen stimulation, naive CD4+ T cells differentiate to several effector or memory cell populations, and cytokines contribute to differentiation outcome. Several proteins on these cells receive costimulatory signals, but a systematic comparison of their differential effects on naive T cell differentiation has not been conducted. Two costimulatory proteins, CD28 and ICAM-1, resident on human naive CD4+ T cells were compared for participation in differentiation. Under controlled conditions, and with no added cytokines, costimulation through either CD3+CD28 or CD3+CAM-1 induced differentiation to T effector and T memory cells. In contrast, costimulation through CD3+ICAM-1 induced differentiation to Treg cells whereas costimulation through CD3+CD28 did not.