SUMMARYPrevious studies have identi®ed a 210 000-molecular weight molecule expressed at a high level on the surface of dendritic cells (DCs) in afferent lymph of cattle and evident on cells with the morphology of DCs in lymphoid tissues. Expression is either absent from other immune cells or is present at a lower level. The molecular weight and cellular distribution suggested that the molecule, called bovine WC6 antigen (workshop cluster), might be an orthologue of human DEC-205 (CD205). To establish whether this was the case, the open reading frame of bovine DEC-205 was ampli®ed, by polymerase chain reaction, from thymic cDNA (accession no. AY264845). The cDNA sequence of bovine DEC-205 had 86% and 78% nucleic acid identity with human and mouse molecules, respectively. COS-7 cells transfected with a plasmid containing the cattle DEC-205 coding region expressed a molecule that stained with WC6-speci®c monoclonal antibody, showing that ruminant WC6 is an orthologue of DEC-205. Twocolour¯ow cytometry of mononuclear cells from afferent lymph draining cattle skin, and from blood, con®rmed the high level of expression on large cells in lymph that were uniformly DC-LAMP positive and major histocompatibility complex class II positive. Within this DC-LAMP population were subpopulations of cells that expressed the mannose receptor or SIRPa. The observations imply that DCs in afferent lymph are all high , but not a uniform population of homogeneous mature DCs.
Recent experimental studies have greatly clarified the function of cell surface molecules in the induction and modulation of T cell responses by antigen-presenting cells (APC). However, the differences in ability to stimulate T cells evident for different types and subpopulations of the same APC, such as dendritic cell subsets, is less well understood. This report details an investigation of an antigen expressed on monocytes that is also expressed on a subset of cattle afferent lymph veiled cells (ALVC). A cDNA library derived from cattle monocytes was screened with monoclonal antibodies (mAb) for expression in COS-7 cells. Using separate mAb for screening, two cDNA were cloned, the sequences of which showed a single long open reading frame encoding a predicted type I glycoprotein of 506 amino acids that contained three immunoglobulin superfamily domains and a long 112-amino acid cytoplasmic tail. We have termed this antigen MyD-1, reflecting its myeloid and dendritic cell distribution. Analysis of the EMBL database revealed that the molecule is a member of the recently described family of signal regulatory proteins (SIRP). The outeremost Ig domain was of the adhesion/receptor I-type, suggesting that MyD-1 might bind to a ligand on another cell. Evidence for this was subsequently obtained by demonstrating that COS-7 cells transfected with MyD-1 cDNA bound CD4 T cells and this binding was blocked by specific mAb. The potential importance of this interaction was supported by the finding that the proliferation of resting memory CD4 T cells to ovalbumin-pulsed monocytes was significantly reduced in the presence of mAb to MyD-1. A role for the molecule in the modulation of the monocyte/dendritic APC response is also predicted from the existence of multiple potential tyrosine phosphorylation sites in the cytoplasmic domain, including the presence of an immunoreceptor tyrosine-based inhibitory motif (ITIM) and the observation that the SIRP alpha family members have been shown to bind to SHP-1 and SHP-2. Together these data indicate a possible functional importance for MyD-1 in the regulation of monocyte and dendritic cell function.
MyD-1 (CD172) is a member of the family of signal regulatory phosphatase (SIRP) binding proteins, which is expressed on human CD14 ؉ monocytes and dendritic cells. We now show a novel role for MyD-1 in the regulation of the innate immune system by pathogen products such as lipopolysaccharide (LPS), purified protein derivative (PPD), and Zymosan. Specifically, we demonstrate that ligation of MyD-1 on peripheral blood mononuclear cells (PBMCs) inhibits tumor necrosis factor alpha (TNF␣) secretion but has no effect on other cytokines induced in response to each of these products. In an attempt to understand the molecular mechanisms underlying this surprisingly selective effect we investigated signal transduction pathways coupled to MyD-1. Ligation of the SIRP was found to recruit the tyrosine phosphatase SHP-2 and promote sequential activation of phosphatidylinositol (PI) 3-kinase, phospholipase D, and sphingosine kinase. Inhibition of LPS-induced TNF␣ secretion by MyD-1 appears to be mediated by this pathway, as the PI 3-kinase inhibitor wortmannin restores normal LPS-driven TNF␣ secretion. MyD-1-coupling to this PI 3-kinasedependent signaling pathway may therefore present a novel target for the development of therapeutic strategies for combating TNF␣ production and consequent inflammatory disease. (Blood. 2003;
Recent experimental studies have greatly clarified the function of cell surface molecules in the induction and modulation of T cell responses by antigen-presenting cells (APC). However, the differences in ability to stimulate T cells evident for different types and subpopulations of the same APC, such as dendritic cell subsets, is less well understood. This report details an investigation of an antigen expressed on monocytes that is also expressed on a subset of cattle afferent lymph veiled cells (ALVC). A cDNA library derived from cattle monocytes was screened with monoclonal antibodies (mAb) for expression in COS-7 cells. Using separate mAb for screening, two cDNA were cloned, the sequences of which showed a single long open reading frame encoding a predicted type I glycoprotein of 506 amino acids that contained three immunoglobulin superfamily domains and a long 112-amino acid cytoplasmic tail. We have termed this antigen MyD-1, reflecting its myeloid and dendritic cell distribution. Analysis of the EMBL database revealed that the molecule is a member of the recently described family of signal regulatory proteins (SIRP). The outeremost Ig domain was of the adhesion/receptor I-type, suggesting that MyD-1 might bind to a ligand on another cell. Evidence for this was subsequently obtained by demonstrating that COS-7 cells transfected with MyD-1 cDNA bound CD4 T cells and this binding was blocked by specific mAb. The potential importance of this interaction was supported by the finding that the proliferation of resting memory CD4 T cells to ovalbumin-pulsed monocytes was significantly reduced in the presence of mAb to MyD-1. A role for the molecule in the modulation of the monocyte/dendritic APC response is also predicted from the existence of multiple potential tyrosine phosphorylation sites in the cytoplasmic domain, including the presence of an immunoreceptor tyrosine-based inhibitory motif (ITIM) and the observation that the SIRP alpha family members have been shown to bind to SHP-1 and SHP-2. Together these data indicate a possible functional importance for MyD-1 in the regulation of monocyte and dendritic cell function.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2025 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.