Structures of CD6 and Its Ligand CD166 Give Insight into Their Interaction

Chappell, Paul E.; Garner, Lee; Yan, Jun; Metcalfe, Clive; Hatherley, Deborah; Johnson, Steven; Robinson, Carol V.; Lea, Susan M.; Brown, Marion H.

doi:10.1016/j.str.2015.05.019

Cited by 52 publications

(76 citation statements)

References 58 publications

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“…Commercially available competing anti CD6 D1 antibody MEM98 [47] showed a positive signal in Iso Ab group (as the receptors are available to bind) and not in Itolizumab treated group (as the receptors are occupied with Itolizumab) (S3A Fig). To further confirm that loss of staining with commercial anti CD6 D1 in Itolizumab treated group (in Panel A) is not because CD6 receptor internalization, staining with fluorochrome conjugated anti-human IgG was performed under the same experimental conditions.…”

Section: Resultsmentioning

confidence: 99%

T cell activation and differentiation is modulated by a CD6 domain 1 antibody Itolizumab

et al. 2017

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CD6 is associated with T-cell modulation and is implicated in several autoimmune diseases. We previously demonstrated that Itolizumab, a CD6 domain 1 (CD6D1) specific humanized monoclonal antibody, inhibited the proliferation and cytokine production by T lymphocytes stimulated with anti-CD3 antibody or when co-stimulated with ALCAM. Aberrant IL-17 producing CD4+ helper T-cells (Th17) have been identified as pivotal for the pathogenesis of certain inflammatory autoimmune disorders, including psoriasis. Itolizumab has demonstrated efficacy in human diseases known to have an IL-17 driven pathogenesis. Here, in in vitro experiments we show that by day 3 of human PBMC activation using anti-CD3 and anti-CD28 co-stimulation in a Th17 polarizing milieu, 15–35% of CD4+ T-cells overexpress CD6 and there is an establishment of differentiated Th17 cells. Addition of Itolizumab reduces the activation and differentiation of T cells to Th17 cells and decreases production of IL-17. These effects are associated with the reduction of key transcription factors pSTAT3 and RORγT. Further, transcription analysis studies in these conditions indicate that Itolizumab suppressed T cell activation by primarily reducing cell cycle, DNA transcription and translation associated genes. To understand the mechanism of this inhibition, we evaluated the effect of this anti-human CD6D1 mAb on ALCAM-CD6 as well as TCR-mediated T cell activation. We show that Itolizumab but not its F(ab’)2 fragment directly inhibits CD6 receptor hyper-phosphorylation and leads to subsequent decrease in associated ZAP70 kinase and docking protein SLP76. Since Itolizumab binds to CD6 expressed only on human and chimpanzee, we developed an antibody binding specifically to mouse CD6D1. This antibody successfully ameliorated the incidence of experimental autoimmune encephalitis in the mice model. These results position CD6 as a key molecule in sustaining the activation and differentiation of T cells and an important target for modulating autoimmune diseases.

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Section: Resultsmentioning

confidence: 99%

T cell activation and differentiation is modulated by a CD6 domain 1 antibody Itolizumab

et al. 2017

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“…Indeed, CD6 is physically associated with the T-cell receptor (TCR) complex (7) and plays relevant roles in regulating some T-cell developmental and activation/differentiation processes (8,9). The latter is achieved mainly through interaction with its main reported ligand, namely, CD166/ALCAM (where ALCAM stands for activated leukocyte cell adhesion molecule)-an adhesion molecule of the immunoglobulin superfamily (10). Aside from such an endogenous ligand, the CD6 ectodomain also interacts with certain PAMPs from G Ϫ (LPS) and G ϩ (LTA and PGN) bacteria (11,12).…”

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confidence: 99%

Protective Effects of Human and Mouse Soluble Scavenger-Like CD6 Lymphocyte Receptor in a Lethal Model of Polymicrobial Sepsis

Martínez-Florensa

Consuegra-Fernández

Aranda

et al. 2017

Antimicrob Agents Chemother

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Sepsis still constitutes an unmet clinical need, which could benefit from novel adjunctive strategies to conventional antibiotic therapy. The soluble form of the scavenger-like human CD6 lymphocyte receptor (shCD6) binds to key pathogenic components from Gram-positive and -negative bacteria and shows time-and dose-dependent efficacy in mouse models of monobacterial sepsis. The objective of the present work was to demonstrate the effectiveness of infusing mouse and human sCD6 by different systemic routes, either alone or as adjunctive therapy to gold standard antibiotics, in a lethal model of polymicrobial sepsis. To this end, C57BL/6 mice undergoing high-grade septic shock induced by cecal ligation and puncture (CLP; Ն90% lethality) were infused via the intraperitoneal (i.p.) or intravenous (i.v.) route with shCD6 at different doses and time points, either alone or in combination with imipenem/cilastatin (I/C) at a dose of 33 mg/kg of body weight every 8 h. Significantly reduced mortality and proinflammatory cytokine levels were observed by i.p. infusion of a single shCD6 dose (1.25 mg/kg) 1 h pre-or post-CLP. When using the i.v. route, mice survival was significantly extended by starting shCD6 infusion at later time points post-CLP (up to 6 h after CLP). Significant adjunctive effects on mouse survival were observed by i.p. or i.v. infusion of shCD6 in combination with i.p. I/C post-CLP. Similar results were obtained in mice expressing high sustained levels (5 to 10 g/ml) of mouse sCD6 in serum by means of transduction with hepatotropic adeno-associated virus (AAV). Taken together, the data support the conserved antibacterial effects of human and mouse sCD6 and their use as adjunctive therapy in experimental models of complex and severe polymicrobial sepsis.KEYWORDS soluble CD6, cecal ligation and puncture, polymicrobial peritonitis, scavenger receptors, sepsis, septic shock, adjunctive therapy S epsis, severe sepsis, and septic shock still present unmet clinical needs with a predicted increase in occurrence and a huge socioeconomic burden as a result of population aging, increases in invasive medical procedures, the emergence of multidrug-resistant (MDR) bacteria, and the increased prevalence of chronic diseases (1). Sepsis is considered a dysregulated systemic inflammatory response syndrome

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“…Structural demonstration of such a complex during interactions between intact cells should be an important goal for future experiments. Early studies of CD6 identified distinct immunologic epitopes that appeared to mediate different functional effects on T cells (38), and more recent work has localized the binding domains on CD6 and CD166 that are involved in the CD6-CD166 interaction (39).…”

Section: Discussionmentioning

confidence: 99%

CD318 is a ligand for CD6

Enyindah-Asonye

Ruth

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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It has been proposed that CD6, an important regulator of T cells, functions by interacting with its currently identified ligand, CD166, but studies performed during the treatment of autoimmune conditions suggest that the CD6-CD166 interaction might not account for important functions of CD6 in autoimmune diseases. The antigen recognized by mAb 3A11 has been proposed as a new CD6 ligand distinct from CD166, yet the identity of it is hitherto unknown. We have identified this CD6 ligand as CD318, a cell surface protein previously found to be present on various epithelial cells and many tumor cells. We found that, like CD6 knockout (KO) mice, CD318 KO mice are also protected in experimental autoimmune encephalomyelitis. In humans, we found that CD318 is highly expressed in synovial tissues and participates in CD6-dependent adhesion of T cells to synovial fibroblasts. In addition, soluble CD318 is chemoattractive to T cells and levels of soluble CD318 are selectively and significantly elevated in the synovial fluid from patients with rheumatoid arthritis and juvenile inflammatory arthritis. These results establish CD318 as a ligand of CD6 and a potential target for the diagnosis and treatment of autoimmune diseases such as multiple sclerosis and inflammatory arthritis.C D6 is a marker of T cells and an important T-cell regulator (1). Recent genome-wide association studies also identified CD6 as a risk gene for multiple sclerosis (MS) (2-5), an autoimmune disease in which T cells play a vital role in the pathogenesis. CD6 is composed of three extracellular domains (domains 1, 2, and 3), and it functions by interacting with its ligand(s) (6). The domain 3 of CD6 has been shown to be the site that the identified CD6 ligand, CD166, also known as ALCAM (activated leukocyte cell adhesion molecule), binds to (7). However, anti-CD166 antibodies only partially blocked the binding of thymic epithelial cells to CD6-overexpressing COS cells, and mAbs blocking CD6-CD166 interactions do not abolish CD6 function (8, 9). Itolizumab, an anti-CD6 mAb developed in Cuba and approved in India for treating psoriasis, reduces pathogenic T-cell responses in patients with psoriasis, but this mAb binds to domain 1 of CD6 instead of domain 3, and it does not interfere with the CD6-CD166 interaction. Interestingly, UMCD6, a mouse antihuman CD6 mAb that we found highly effective in treating encephalomyelitis (EAE) in CD6 humanized mice, also fails to block the CD6-CD166 interaction. All these studies suggest the existence of an additional CD6 ligand, other than CD166, that binds to domain 1 of CD6, and could be critical for CD6 function in autoimmune conditions. Further studies using a CD6 fusion protein as a bait to pull down CD6-binding proteins from synovial fibroblast surface proteins showed the binding of three polypeptides (10). One of these polypeptides was identified as CD166, and the identities of the other two were unknown (11). A mAb termed 3A11 was developed, and the antigen recognized by this mAb was identified as the new ligand of ...

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Structures of CD6 and Its Ligand CD166 Give Insight into Their Interaction

Cited by 52 publications

References 58 publications

T cell activation and differentiation is modulated by a CD6 domain 1 antibody Itolizumab

T cell activation and differentiation is modulated by a CD6 domain 1 antibody Itolizumab

Protective Effects of Human and Mouse Soluble Scavenger-Like CD6 Lymphocyte Receptor in a Lethal Model of Polymicrobial Sepsis

CD318 is a ligand for CD6

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