anti-human L-Selectin (CD62L)

anti-human L-Selectin (CD62L) (Clone: DREG-56)

 

Rissiek, A., et al. (2015). “The expression of CD39 on regulatory T cells is genetically driven and further upregulated at sites of inflammation.” J Autoimmun 58: 12-20. PubMed

Regulatory T cells (Tregs) use different mechanisms to exert their suppressive function, among them the conversion of ATP to adenosine initiated by the ectonucleotidase CD39. In humans, the expression of CD39 on Tregs shows a high interindividual variation, and is especially high at sites of inflammation, like the synovia of patients with arthritis. How CD39 expression is regulated, and the functional consequences of different levels of CD39 expression is not known. We show here that stimulation of CD39(-) Tregs results in a modest upregulation of CD39, which cannot explain the high levels observed in many donors. Moreover, CD39(+) Tregs are present in naive compartments such as cord blood and thymus, and the individual frequency of CD39(+) Tregs remains stable over time, suggesting inherent regulation of CD39 expression. Indeed, we show that a single nucleotide polymorphism in the CD39 gene determines expression levels in Tregs. CD39(+) Tregs suppress T cell proliferation and inflammatory cytokine production more efficiently than CD39(-) Tregs. Accordingly, Tregs from donors with the GG (high CD39) genotype have a higher capacity to suppress IFN-gamma and IL-17 production by effector cells than Tregs from AA (low CD39) donors. Our study demonstrates that the expression of CD39 in Tregs is primarily genetically driven, and this may determine interindividual differences in the control of inflammatory responses.

 

Auvinen, K., et al. (2014). “Expression and function of endothelial selectins during human development.” Immunology 143(3): 406-415. PubMed

Leucocyte trafficking is vital for the immune defence. In adults, early tethering and rolling interactions between leucocytes and endothelial cells are mediated by P-, E- and L-selectins and their ligands. In contrast, the role of selectins in migration of mononuclear cells during fetal development in humans remains unknown. We studied the functions of endothelial E- and P-selectins and their counter-receptors during human ontogeny. Immunohistochemical stainings showed that P-selectin is expressed in megakaryocytes and endothelial cells starting from gestational weeks 7 and 11, respectively. Endothelial E-selectin appeared latest, at week 32. Real-time imaging using in vitro flow chamber assays showed that cord blood mononuclear leucocytes used E-, P- and L-selectin and PSGL-1 to roll on and adhere to endothelium under physiological shear stress. These data show that selectins are synthesized and functional before birth in humans and have the potential to mediate the emigration of mononuclear cells and inflammatory responses.

 

Myklebust, J. H., et al. (2013). “High PD-1 expression and suppressed cytokine signaling distinguish T cells infiltrating follicular lymphoma tumors from peripheral T cells.” Blood 121(8): 1367-1376. PubMed

Defects in T-cell function in patients with cancer might influence their capacity to mount efficient antitumor immune responses. Here, we identified highly reduced IL-4-, IL-10-, and IL-21-induced phosphorylation of STAT6 and STAT3 in tumor-infiltrating T cells (TILs) in follicular lymphoma (FL) tumors, contrasting other non-Hodgkin lymphoma TILs. By combining phospho-protein-specific flow cytometry with several T-cell markers, we identified that CD4(+)CD45RO(+)CD62L(-) FL TILs were largely nonresponsive to cytokines, in contrast to the corresponding autologous peripheral blood subset. We observed differential expression of the inhibitory receptor PD-1 in FL TILs and peripheral blood T cells. Furthermore, CD4(+)PD-1(hi) FL TILs, containing T(FH) and non-T(FH) cells, had lost their cytokine responsiveness, whereas PD-1 TILs had normal cytokine signaling. However, this phenomenon was not tumor specific, because tonsil T cells were similar to FL TILs. FL tumor cells were negative for PD-1 ligands, but PD-L1(+) histiocytes were found within the T cell-rich zone of the neoplastic follicles. Disruption of the microenvironment and in vitro culture of FL TILs could restore cytokine signaling in the PD-1(hi) subset. Because FL TILs in vivo probably receive suppressive signals through PD-1, this provides a rationale for testing PD-1 Ab in combination with immunotherapy in patients with FL.

 

Forlow, S. B., et al. (2000). “Leukocyte-leukocyte interactions mediated by platelet microparticles under flow.” Blood 95(4): 1317-1323. PubMed

Platelet microparticles (PMPs) are released from activated platelets and express functional adhesion receptors, including P-selectin, on their surface. PMP concentrations are elevated in many disorders, and their role in accelerating coagulation has been studied. However, their role in leukocyte aggregation has not been defined. We hypothesized that P-selectin-expressing PMPs bridge leukocytes that express P-selectin glycoprotein ligand-1 (PSGL-1), thereby allowing them to interact under flow conditions. PMPs were isolated from platelet-rich plasma or were generated by activating washed platelets with calcium ionophore. PMPs increased transient adhesion of flowing HL-60 cells or neutrophils to HL-60 cells or neutrophils prebound to the surface of a parallel plate flow chamber. Homotypic neutrophil interactions are initiated by the binding of L-selectin to PSGL-1. However, even when L-selectin function was blocked, PMPs allowed flowing neutrophils to aggregate and to interact with PSGL-1-expressing cells prebound to the surface of the flow chamber. The microparticle-mediated cell interactions occurred at lower shear stresses than those mediated by L-selectin. PMPs may enhance leukocyte aggregation and leukocyte accumulation on selectin-expressing substrates, especially in diseases where the concentration of the particles is elevated. (Blood. 2000;95:1317-1323)

 

Kishimoto, T. K., et al. (1990). “Identification of a human peripheral lymph node homing receptor: a rapidly down-regulated adhesion molecule.” Proc Natl Acad Sci U S A 87(6): 2244-2248. PubMed

Lymphocyte migration to lymphoid organs involves organ-specific homing receptors. The mouse peripheral lymph node homing receptor, defined by the MEL-14 monoclonal antibody (mAb), is a lectin-like cell surface protein, which is rapidly down-regulated upon cell activation with phorbol 12-myristate 13-acetate. We have raised mAbs against rapidly shed molecules released from the cell surface of activated human leukocytes. Five mAbs, DREG-55, -56, -110, -152, and -200, define an 80- to 85-kDa molecule involved in human lymphocyte recognition of peripheral lymph node (PLN) high endothelial venules (HEVs). The DREG-56 mAb specifically inhibits greater than 90% of binding of human lymphocytes to HEVs within frozen sections of peripheral but not mucosal lymphoid tissue. Furthermore, the gp80 antigen is expressed on lymphoid cell lines that are capable of binding to PLN HEVs. The DREG-56 mAb also inhibits lymphocyte binding of the phosphomannan monoester core from Hansenula hostii Y-2448, an activity associated with human and mouse lymphocyte recognition of PLN HEVs. Finally, all five DREG mAbs specifically stain COS cells transfected with LAM-1 cDNA, a putative human homologue of mouse MEL-14 antigen. These results demonstrate that the DREG mAbs define a human lymphocyte homing receptor for PLN HEVs and indicate that this human antigen is homologous to the MEL-14-defined murine lymphocyte homing receptor.