The B7 family member programmed death ligand 2 (PD-L2) has been implicated in both positive and negative regulation of T cell activity. In this study, we demonstrate that on human T cells, PD-L2 acts only as a negative regulator of T cell activity, inhibiting proliferation, IL-2 production, and IFN-c production via its interaction with programmed death-1 (PD-1). This study also shows a novel role for PD-1 in inhibiting b1 and b2 integrin-mediated adhesion. PD-L2 inhibition of T cell function involves modulation of the phosphoinositide 3-OH kinase (PI 3-K)/AKT and extracellular signalrelated kinase (ERK)/mitogen-activated protein kinase (MAPK) pathways, with PD-L2 inhibiting anti-CD3-induced AKT phosphorylation within minutes and ERK phosphorylation after hours. Analysis of phosphatase activity of Src homology 2 domaincontaining tyrosine phosphatase (SHP)-1 and SHP-2 in response to anti-CD3 mAb or anti-CD3 mAb + PD-L2 stimulation revealed that while SHP-1 phosphatase activity is not affected by stimulation, SHP-2 phosphatase activity is significantly increased by anti-CD3 mAb + PD-L2 stimulation. Anti-CD3 mAb + PD-L2 stimulation also increased the level of SHP-2 associated with the PD-1 receptor. These results suggest that catalytically active SHP-2 associated with the PD-1 receptor is involved in modulating T cell function. IntroductionMembers of the B7:CD28 superfamily play a critical role in providing signals that co-stimulate or co-inhibit T cell activation [1, 2, 3]. T cells express the co-stimulators CD28 and inducible co-stimulator (ICOS) as well as the co-inhibitors CTL-associated antigen (CTLA-4) and programmed death-1 (PD-1). While CD28 is present on both naive and activated T cells, ICOS is found only on activated T cells. Both CD28 and ICOS enhance TCR/ CD3-induced proliferation and cytokine production. The co-inhibitors CTLA-4 and PD-1 are expressed on activated T cells, inhibiting TCR/CD3-induced proliferation and cytokine production [1, 2].A potential point at which co-inhibition and costimulation converge is at the level of programmed death ligand 2 (PD-L2 or B7-DC). PD-L2 has been shown to bind to PD-1. On both human and mouse T cells, ligation of PD-1 by PD-L2 inhibits TCR/CD3-induced proliferation and cytokine production [3][4][5][6]. In mice, PD-L2 participates in co-stimulation. Stimulation of mouse CD4 + T cells in vitro with PD-L2/Fc enhances anti-CD3-induced proliferation and IL-2 and IFN-c production [7]. Transfection of tumor cells with PD-L2 promotes CD8 + T cell-mediated tumor rejection, and CD8 + T cells lacking PD-1 expression still bind PD-L2 [8]. Additionally, PD-L2 enhances anti-CD3-and anti-CD3/B7-1-Ig-induced CD4 + T cell proliferation and IL-2 and IFN-c production in PD-1-deficient mice, indicating a potential for other unidentified co-stimulatory receptor(s) for PD-L2 [9]. While it is well established that B7:CD28 family members play a critical role in regulating T cell proliferation and cytokine production, there is also evidence that these receptors are involved in regulatin...

This paper deals with the collection, fractionation and partial characterization of the slime gland secretion of the Pacific hagfish (Eptatretus stouti) with emphasis on the mucous fraction. Secretions were collected by electrical stimulation of the glands of anesthetized hagfish and, using three different methods, separated into three fractions: 1) the thread cells, 2) the mucous vesicles of the mucous cells, and 3) the soluble fraction. The methods take advantage of the stabilization of the thread cells and mucous vesicles by ammonium sulfate and sodium citrate.

Microvessels were isolated from canine cerebral cortex, and the composition of the endothelial cell membrane was investigated. Endothelial cell membranes were separated from the surrounding basement membrane, solubilized, and subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis in 12% gels. Staining with Coomassie Blue revealed a characteristic banding pattern of at least 12 major proteins with apparent molecular weights between 14,000 and 250,000. When proteins from red blood cell ghosts were run simultaneously, no similarities were observed, except for proteins at apparent molecular weights of 43,000 (band 3) and 35,000 (band 4). These two proteins migrated exactly to the positions of the erythrocyte proteins actin and glyceraldehyde 3-phosphate dehydrogenase, respectively. Membrane glycoproteins in gels were also examined by the use of fluorescent lectins. Of the fluorescein isothiocyanate-conjugated (FITC) lectins tested, only FITC-concanavalin A had an affinity for any membrane components. Diazotized [125I]iodosulfanilic acid, a membrane-impermeable reagent, was used to label the internal (lumen) cell surface and the external (antilumen) cell surface. Autoradiography and determination of radioactivity levels in gel slices showed that several proteins were specifically labeled, and that major differences in radioactivity of proteins existed in internal and external labeling experiments. It is concluded that the protein composition of the luminal membrane is different from that of the antiluminal membrane.

No abstract