CD43 – One molecule, many tales to recount

CD43 in the malignant flow cytometry laboratory in 2020

Objectives: CD43 can be useful in routine flow cytometry. We conducted a systematic review aiming to describe when CD43 is used by flow cytometry in malignant hematology and to determine its value in these settings. Methods: Systematic review of MEDLINE (search 'CD43' AND 'flow cytometry,' starting in 2010). Results: Twenty-one of 103 entries retrieved were included in this systematic review. CD43 is used in three settings: 1) in the classification of mature B cell lymphoproliferative disorders, 2) as part of a strategy to quantify residual disease in chronic lymphocytic leukemia (CLL) and 3) to help classify CD10-positive B cell populations. In this section, the published data is summarized, the clinical usefulness in each of these settings is evaluated and illustrative cases are shown. Conclusion: CD43 has a growing role in the diagnosis and management of B cell malignancies; it has become essential for the classification of B cell lymphoproliferative disorders and may be of help in the differential diagnosis of CD10-positive lymphomas by FC. It is also required for optimal quantification of CLL residual disease, which will soon be used to guide therapeutic decisions.

Sialomucin CD43 regulates T helper type 17 cell intercellular adhesion molecule 1 dependent adhesion, apical migration and transendothelial migration

T helper type 17 lymphocytes (Th17 cells) infiltrate the central nervous system (CNS), induce inflammation and demyelination and play a pivotal role in the pathogenesis of multiple sclerosis. Sialomucin CD43 is highly expressed in Th17 cells and mediates adhesion to endothelial selectin (E-selectin), an initiating step in Th17 cell recruitment to sites of inflammation. CD43^-/- mice have impaired Th17 cell recruitment to the CNS and are protected from experimental autoimmune encephalomyelitis (EAE), the mouse model of multiple sclerosis. However, E-selectin is dispensable for the development of EAE, in contrast to intercellular and vascular cell adhesion molecules (ICAM-1 and VCAM-1). We report that CD43^-/- mice have decreased demyelination and T-cell infiltration, but similar up-regulation of ICAM-1 and VCAM-1 in the spinal cord, compared with wild-type (WT) mice, at the initiation of EAE. CD43^-/- Th17 cells have impaired adhesion to ICAM-1 under flow conditions in vitro, despite having similar expression of LFA-1, the main T-cell ligand for ICAM-1, as WT Th17 cells. Regardless of the route of integrin activation, CD43^-/- Th17 cell firm arrest on ICAM-1 was comparable to that of WT Th17 cells, but CD43^-/- Th17 cells failed to optimally apically migrate on immobilized ICAM-1-coated coverslips and endothelial cells, and to transmigrate under shear flow conditions in an ICAM-1-dependent manner. Collectively, these findings unveil novel roles for CD43, facilitating adhesion of Th17 cells to ICAM-1 and modulating apical and transendothelial migration, as mechanisms potentially responsible for Th17 cell recruitment to sites of inflammation such as the CNS.

Coexpression of CD5 and CD43 predicts worse prognosis in diffuse large B-cell lymphoma

Both CD5 and CD43 are expressed on the surface of B lymphocytes of definite phase and associated with the adverse outcome in diffuse large B-cell lymphoma (DLBCL). However, the relationship between CD5 and CD43 expression and the prognostic value of CD5/CD43 coexpression in DLBCL are unknown. We herein determined the correlation between CD5 and CD43 expression, as separate factors or in combination, with the clinicopathological features and survival of 200 patients with DLBCL receiving standard chemotherapy with or without rituximab. Among these DLBCL patients, CD5 expression, CD43 expression, and CD5/CD43 coexpression were detected in 18 (9%), 57 (27%), and 10 (5%) patients, respectively, and all were positively correlated with advanced age and nongerminal cell type. CD5-positive and CD43-positive DLBCL patients had poorer event-free survival (EFS, P < 0.001) and overall survival (OS, P < 0.001) than CD5-negative and CD43-negative patients, respectively. CD5/CD43 coexpression was correlated with a significantly worse prognosis than CD5 or CD43 expression alone. Univariate analysis showed that CD5 expression, CD43 expression, and CD5/CD43 coexpression were all adverse prognostic factors for DLBCL patient survival, and CD5/CD43 coexpression was associated with a greater relative risk for recurrence and death than either CD5 or CD43 expression alone. Multivariate analysis demonstrated that CD5/CD43 coexpression was an independent prognostic factor for EFS (P < 0.001) and OS (P < 0.001) in DLBCL. In conclusion, our data indicate that DLBCL patients with CD5/CD43 coexpression represent a specific subgroup with a significantly worse prognosis than those expressing either marker alone.

Aberrant expression of interleukin-10 and activation-induced cytidine deaminase in B cells from patients with Behçet's disease

Despite extensive studies, the pathogenesis of Behçet's disease (BD) remains unclear. In particular, the roles of B cells in patients with BD have not been elucidated. Activation-induced cytidine deaminase (AID) is a critical enzyme for immunoglobulin (Ig) heavy chain class switching and somatic hypermutation in B cells and the abnormal expression of AID in various immune conditions has previously been studied. B10 cells, an interleukin (IL)-10-secreting subset of regulatory B cells, function to downregulate inflammation and autoimmunity. Thus, in the present study, the relevance of B cells in patients with BD was investigated. The plasma levels of IL-10 and IgA and the proportions of cluster of differentiation (CD)43+ B cells, excluding naïve B cells, were measured in 16 patients with BD and 16 age- and sex-matched healthy controls (HCs). Additionally, the mRNA levels of IL-10 and AID were assessed in B cells from fresh peripheral blood samples of the BD patients and HCs. The plasma level of IL-10 in patients with BD did not differ significantly from that in HCs. Similarly, there was no significant difference in the plasma level of IgA, although a slight increase was observed in patients with BD compared with that in HCs. There were no differences in CD43+CD19+ B cell numbers between patients with BD and HCs. However, IL-10 mRNA levels were significantly reduced (P<0.05), while AID mRNA levels were significantly increased (P<0.01) in the B cells of patients with BD compared with those in HCs. These results provide insight into the role of B cells in patients with BD.

T cell acute lymphoblastic leukemia (T-ALL): New insights into the cellular origins and infiltration mechanisms common and unique among hematologic malignancies

T-cell acute lymphoblastic leukemia (T-ALL) accounts for 15% and 25% of total childhood and adult ALL cases, respectively. During T-ALL, patients are at risk of organ infiltration by leukemic T-cells. Infiltration is a major consequence of disease relapse and correlates with poor prognosis. Transendothelial migration of leukemic cells is required to exit the blood stream into target organs. While mechanisms of normal T-cell transmigration are well known, the mechanisms of leukemic T-cell extravasation remain elusive; but involvement of chemokines, integrins and Notch signaling play critical roles. Here, we summarize current knowledge about molecular mechanisms of leukemic T-cell infiltration with special emphasis on the newly identified subtype early T-cell-progenitor (ETP)-ALL. Furthermore, we compare the extravasation potential of T-ALL cells with that of other hematologic malignancies such as B-ALL and acute myeloid leukemia (AML).

Interaction of the CD43 Sialomucin with the Mycobacterium tuberculosis Cpn60.2 Chaperonin Leads to Tumor Necrosis Factor Alpha Production

Mycobacterium tuberculosis is the causal agent of tuberculosis. Tumor necrosis factor alpha (TNF-α), transforming growth factor β (TGF-β), and gamma interferon (IFN-γ) secreted by activated macrophages and lymphocytes are considered essential to contain Mycobacterium tuberculosis infection. The CD43 sialomucin has been reported to act as a receptor for bacilli through its interaction with the chaperonin Cpn60.2, facilitating mycobacterium-macrophage contact. We report here that Cpn60.2 induces both human THP-1 cells and mouse-derived bone marrow-derived macrophages (BMMs) to produce TNF-α and that this production is CD43 dependent. In addition, we present evidence that the signaling pathway leading to TNF-α production upon interaction with Cpn60.2 requires active Src family kinases, phospholipase C-γ (PLC-γ), phosphatidylinositol 3-kinase (PI3K), p38, and Jun N-terminal protein kinase (JNK), both in BMMs and in THP-1 cells. Our data highlight the role of CD43 and Cpn60.2 in TNF-α production and underscore an important role for CD43 in the host-mycobacterium interaction.

CD43 Functions as an E-Selectin Ligand for Th17 Cells In Vitro and Is Required for Rolling on the Vascular Endothelium and Th17 Cell Recruitment during Inflammation In Vivo

Endothelial E- and P-selectins mediate lymphocyte trafficking in inflammatory processes by interacting with lymphocyte selectin ligands. These are differentially expressed among different T cell subsets and function alone or in cooperation to mediate T cell adhesion. In this study, we characterize the expression and functionality of E-selectin ligands in Th type 17 lymphocytes (Th17 cells) and report that CD43 functions as a Th17 cell E-selectin ligand in vitro that mediates Th17 cell rolling on the vascular endothelium and recruitment in vivo. We demonstrate Th17 cells express CD44, P-selectin glycoprotein ligand (PSGL)-1, and CD43. Few PSGL-1(-/-)CD43(-/-) Th17 cells accumulated on E-selectin under shear flow conditions compared with wild-type cells. CD43(-/-) Th17 cell accumulation on E-selectin was impaired as compared with wild-type and PSGL-1(-/-), and similar to that observed for PSGL-1(-/-)CD43(-/-) Th17 cells, indicating that CD43 alone is a dominant ligand for E-selectin. Notably, this finding is Th17 cell subset specific because CD43 requires cooperation with PSGL-1 in Th1 cells for binding to E-selectin. In vivo, Th17 cell recruitment into the air pouch was reduced in CD43(-/-) mice in response to CCL20 or TNF-α, and intravital microscopy studies demonstrated that CD43(-/-) Th17 cells had impaired rolling on TNF-α-treated microvessels. Furthermore, CD43(-/-) mice were protected from experimental autoimmune encephalomyelitis and had impaired recruitment of Th17 cells in the spinal cord. Our findings demonstrate that CD43 is a major E-selectin ligand in Th17 cells that functions independent of PSGL-1, and they suggest that CD43 may hold promise as a therapeutic target to modulate Th17 cell recruitment.

CD43 expression in diffuse large B-cell lymphoma, not otherwise specified: CD43 is a marker of adverse prognosis

CD43 (leukosialin) is a transmembrane glycoprotein expressed in a variety of hematopoietic cells, including B lymphocytes, and a variety of malignancies including lymphoma, leukemia, and solid tumors. CD43 plays an important role in the development of many diseases, and coexpression of CD43 and CD20 on peripheral B cells is a predictive factor of hematopoietic malignancy. Although CD43 is expressed in approximately 25% of diffuse large B-cell lymphomas (DLBCLs), its prognostic significance remains unclear. To analyze CD43 expression in DLBCL, not otherwise specified (DLBCL, NOS), and assess its prognostic value, we analyzed clinical data from 160 patients with DLBCL, NOS. We observed that CD43 expression was detected in 47 (29.4%) of 160 cases. CD43 expression was positively correlated with old age (>60 years), high serum lactate dehydrogenase level, B symptoms, non-germinal center type, and DLBCL, NOS, mortality. Patients with CD43-positive DLBCL, NOS, had poorer overall survival (P < .001, log-rank test) and event-free survival (P < .001, log-rank test) than CD43-negative patients. Univariate analysis showed that CD43 expression, age, sex, Ann Arbor stage, International Prognostic Index category, and germinal center phenotype were prognostic factors for DLBCL, NOS, patient survival. Multivariate analysis showed that CD43 expression was an independent significant prognostic factor for event-free survival (P < .001) and overall survival (P < .001). Based on these data, we conclude that CD43 expression is a novel adverse prognostic factor for patients with DLBCL, NOS.

Aberrant glycosylation as biomarker for cancer: focus on CD43

Glycosylation is a posttranslational modification of proteins playing a major role in cell signalling, immune recognition, and cell-cell interaction because of their glycan branches conferring structure variability and binding specificity to lectin ligands. Aberrant expression of glycan structures as well as occurrence of truncated structures, precursors, or novel structures of glycan may affect ligand-receptor interactions and thus interfere with regulation of cell adhesion, migration, and proliferation. Indeed, aberrant glycosylation represents a hallmark of cancer, reflecting cancer-specific changes in glycan biosynthesis pathways such as the altered expression of glycosyltransferases and glycosidases. Most studies have been carried out to identify changes in serum glycan structures. In most cancers, fucosylation and sialylation are significantly modified. Thus, aberrations in glycan structures can be used as targets to improve existing serum cancer biomarkers. The ability to distinguish differences in the glycosylation of proteins between cancer and control patients emphasizes glycobiology as a promising field for potential biomarker identification. In this review, we discuss the aberrant protein glycosylation associated with human cancer and the identification of protein glycoforms as cancer biomarkers. In particular, we will focus on the aberrant CD43 glycosylation as cancer biomarker and the potential to exploit the UN1 monoclonal antibody (UN1 mAb) to identify aberrant CD43 glycoforms.

CD43 signals prepare human T cells to receive cytokine differentiation signals

T cells are increasingly used for passive immunotherapy and bone marrow transplantation. Proper ex-vivo management of the cells is important for the desired therapeutic effects. For differentiation into effector cells of the Th1 and Th2 phenotypes, T-cells require signals from IFNγ and IL-4, respectively. Naïve cells have an extremely low expression of the specific receptors that recognize these cytokines, indicating that in order to differentiate, cells need to perceive other signals that will enable them to sense the cytokine milieu. CD43 has been proposed as one of the molecules that make the initial contacts with antigen presenting cells. We report here that in cord blood, adult naïve and total human T cells, CD43 signals induced the expression of both IFNγ and IL-4 receptors, mediate their capping, increased their signaling and augmented differentiation mediated by these receptors. CD43 signals also stimulated the expression of IFNγ and in neonatal cells that of IL-4 as well. These data demonstrate an important role for CD43 signals in T-cell preparedness for differentiation into effector cells.

CD43 promotes cells transformation by preventing merlin-mediated contact inhibition of growth

In normal tissues, strict control of tissue size is achieved by regulating cell numbers. The mechanism that controls total cell number is known as contact inhibition of growth and it depends on the NF2/Merlin pathway. Negative regulation of this pathway by deleterious mutations or by oncogenes results in cell transformation and tumor progression. Here we provide evidence that the CD43 sialomucin cooperates with oncogenic signals to promote cell transformation by abrogating the contact inhibition of growth through a molecular mechanism that involves AKT-dependent Merlin phosphorylation and degradation. Accordingly, inhibition of endogenous CD43 expression by RNA interference in lung, cervix and colon human cancer cells impaired tumor growth in vivo. These data underscore a previously unidentified role for CD43 in non-hematopoietic tumor progression.