Serum Levels of Soluble CD26/Dipeptidyl Peptidase-IV in Type 2 Diabetes Mellitus and Its Association with Metabolic Syndrome and Therapy with Antidiabetic Agents in Malaysian Subjects

BackgroundA soluble form of CD26/dipeptidyl peptidase-IV (sCD26/DPP-IV) induces DPP-IV enzymatic activity that degrades incretin. We investigated fasting serum levels of sCD26/DPP-IV and active glucagon-like peptide-1 (GLP-1) in Malaysian patients with type 2 diabetes mellitus (T2DM) with and without metabolic syndrome (MetS), as well as the associations between sCD26/DPP-IV levels, MetS, and antidiabetic therapy.MethodsWe assessed sCD26/DPP-IV levels, active GLP-1 levels, body mass index (BMI), glucose, insulin, A1c, glucose homeostasis indices, and lipid profiles in 549 Malaysian subjects (including 257 T2DM patients with MetS, 57 T2DM patients without MetS, 71 non-diabetics with MetS, and 164 control subjects without diabetes or metabolic syndrome).ResultsFasting serum levels of sCD26/DPP-IV were significantly higher in T2DM patients with and without MetS than in normal subjects. Likewise, sCD26/DPP-IV levels were significantly higher in patients with T2DM and MetS than in non-diabetic patients with MetS. However, active GLP-1 levels were significantly lower in T2DM patients both with and without MetS than in normal subjects. In T2DM subjects, sCD26/DPP-IV levels were associated with significantly higher A1c levels, but were significantly lower in patients using monotherapy with metformin. In addition, no significant differences in sCD26/DPP-IV levels were found between diabetic subjects with and without MetS. Furthermore, sCD26/DPP-IV levels were negatively correlated with active GLP-1 levels in T2DM patients both with and without MetS. In normal subjects, sCD26/DPP-IV levels were associated with increased BMI, cholesterol, and LDL-cholesterol (LDL-c) levels.ConclusionSerum sCD26/DPP-IV levels increased in T2DM subjects with and without MetS. Active GLP-1 levels decreased in T2DM patients both with and without MetS. In addition, sCD26/DPP-IV levels were associated with Alc levels and negatively correlated with active GLP-1 levels. Moreover, metformin monotherapy was associated with reduced sCD26/DPP-IV levels. In normal subjects, sCD26/DPP-IV levels were associated with increased BMI, cholesterol, and LDL-c.     

Aqueous seed extract of Syzygium cumini inhibits the dipeptidyl peptidase IV and adenosine deaminase activities, but it does not change the CD26 expression in lymphocytes in vitro

Syzygium cumini (Sc) have been intensively studied in the last years due its beneficial effects including anti-diabetic and anti-inflammatory potential. Thus, the aim of this study was to evaluate the effect of aqueous seed extract of Sc (ASc) in the activity of enzymes involved in lymphocyte functions. To perform this study, we isolated lymphocytes from healthy donors. Lymphocytes were exposed to 10, 30, and 100 mg/mL of ASc during 4 and 6 h and adenosine deaminase (ADA), dipeptidyl peptidase IV (DPP-IV), and acetylcholinesterase (AChE) activities as well as CD26 expression and cellular viability were evaluated. ASc inhibited the ADA and DPP-IV activities without alteration in the CD26 expression (DPP-IV protein). No alterations were observed in the AChE activity or in the cell viability. These results indicate that the inhibition of the DPP-IV and ADA activities was dependent on the time of exposition to ASc. We suggest that ASc exhibits immunomodulatory properties probably via the pathway of DPP-IV–ADA complex, contributing to the understanding of these proceedings in the purinergic signaling.     

CD26 Expression on T Helper Populations and sCD26 Serum Levels in Patients with Rheumatoid Arthritis

We studied dipeptidyl peptidase IV (DPP-IV, CD26) expression in different T helper cells and serum soluble DPP-IV/sCD26 levels in rheumatoid arthritis (RA) patients, correlated these with disease activity score (DAS), and examined how they were affected by different therapies, conventional or biological (anti-TNF, anti-CD20 and anti-IL6R or Ig-CTLA4). The percentage of CD4⁺CD45R0⁺CD26^- cells was greatly reduced in patients (up to 50%) when compared with healthy subjects. Three other subsets of CD4 cells, including a CD26high Th1-associated population, changed variably with therapies. Data from these subsets (frequency and staining density) significantly correlated with DAS28 or DAS28 components but different in each group of patients undergoing the different therapies. Th17 and Th22 subsets were implicated in RA as independent CCR4⁺ and CCR4^- populations each, with distinct CD26 expression, and were targeted with varying efficiency by each therapy. Serum DPP-IV activity rather than sCD26 levels was lower in RA patients compared to healthy donors. DPP-IV and sCD26 serum levels were found related to specific T cell subsets but not to disease activity. We conclude that, according to their CD26 expression, different cell subsets could serve to monitor RA course, and an uncharacterized T helper CD26^- subset, not targeted by therapies, should be monitored for early diagnosis.     

The adenosine deaminase-binding region is distinct from major anti-CD26 mAb epitopes on the human dipeptidyl peptidase IV(CD26) molecule

CD26 or dipeptidyl peptidase IV (DPP-IV) is a cell surface protease involved in T cell activation. Monoclonal antibodies (mAbs) directed against the CD26 molecule are able to stimulate CD26-expressing T cells. Although many different CD26-specific mAbs exist which are able to provide a triggering signal in T cells, little is known about their specific epitopes on the CD26 molecule. Whereas some mAbs were shown to compete with each other and to inhibit the association of adenosine deaminase (ADA) and human immunodeficiency virus 1 (HIV-1)-derived Tat protein with CD26, other CD26-specific mAbs obviously bind to distinct regions on DPP-IV. In the present study we have generated truncated versions of the human CD26 molecule and expressed them in COS-1 cells to study the binding pattern of a panel of 14 CD26-specific mAbs in confocal microscopy and, thus, correlated the CD26-specific mAbs epitopes with the binding region of ADA. We show that the majority of anti-CD26 mAbs is directed against the glycosylation-rich region of the molecule whereas the ADA-binding site could be located in the cysteine-rich region of DPP-IV. In contrast to binding experiments with purified ADA, which revealed a specific association with CD26 on CD26-positive Jurkat cells, HIV-derived Tat protein did not interact specifically with CD26 on transfected Jurkat cells, nor could Tat binding be competed by anti-CD26-specific mAbs.     

Expression of the rat CD26 antigen (dipeptidyl peptidase IV) on subpopulations of rat lymphocytes.

The T cell activation antigen CD26 has been recently identified as the cell surface ectopeptidase dipeptidyl peptidase IV (DPP-IV). DPP-IV is found on many cell types, including lymphocytes, epithelial cells, and certain endothelial cells. The MRC OX61 monoclonal antibody (MAb) which specifically recognises rat DPP-IV was used to examine the expression of CD26/DPP-IV on rat lymphocytes. The molecular nature of the antigen was examined by immunoprecipitation from thymocytes, splenocytes, and hepatocytes. Analysis by one- and two-dimensional gel electrophoresis indicated that the native form of CD26 includes a 220-kDa homodimer. On tissue sections MRC OX61 MAb stained nearly all thymocytes and in the spleen and lymph nodes predominantly stained the T cell areas. However, in immunofluorescence experiments OX61 stained 80 to 87% of lymph node cells and 78 to 85% of spleen cells. Furthermore, two-colour immunofluorescence analysis of the CD4+, CD8+, and Ig+ lymphocyte subsets indicated that only 2 to 5% of each of these subsets lacked OX61 staining. Spleen cells and thymocytes of both CD4+ and CD8+ subsets stained much more intensely with OX61 after these cells were stimulated with phytohemagglutinin. These findings indicate that rat CD26 antigen expression is not confined to the T cell population as has been suggested, but also occurs on B cells, and is increased on T cells following their activation.     

Correlation between heat shock proteins,adiponectin, and T lymphocyte cytokine expression in type 2 diabetics

Type 2 diabetes mellitus (T2DM) features insulin resistance, hyperglycemia, dyslipidemia, overproduction of inflammatory cytokines, and systemic oxidative stress. Here, heat shock proteins Hsp70 and Hsp 90, adiponectin, and heme oxygenase-1 (HO-1, Hsp32) are profiled in peripheral blood mononuclear cells (PBMC) and serum from 25 T2DM patients and 25 healthy control subjects. Cells cultured with phorbol 12-myristate 13-acetate/ionomycin were evaluated by three-color flow cytometry for immunophenotypic biomarkers. Plasma HO-1, Hsp, and adiponectin levels were assayed by enzyme-linked immunosorbent assay (ELISA). Relative to healthy controls, T2DM patients exhibited significantly elevated plasma Hsp70, and representation of T helper immunophenotypes activated to express inflammatory cytokines, including CD4+ IFN-γ+, CD4+ TNF-α+, CD4+ IL-6+, CD4+ IL-1β+ T cells, significantly lower representation of CD4+ IL-10+ T cells, plasma adiponectin and cell-associated HO-1 expression—with no significant differences in plasma Hsp90 between T2DM and healthy controls. Plasma HO-1 and adiponectin in T2DM patients inversely correlated with TNF-α and showed inverse correlation between serum LDL and plasma HO-1. Moreover, TNF-α and Hsp90 in T2DM patients correlated positively with fasting blood glucose (FBG). These results demonstrate correlation between potentially pathogenic T cells, HO-1, and adiponectin, additionally revealing a T helper (Th)1-related character of T2DM immunopathogenesis, suggesting potential for novel T cell-related management strategies for T2DM and related co-morbidities.     

Circulating expression levels of CircHIPK3 and CDR1as circular-RNAs in type 2 diabetes patients

Background

Recent investigations suggested that deregulated levels of Circular RNAs (circRNAs) could be associated with type 2 diabetes mellitus (T2DM) pathogenesis. Accordingly, this study aimed to determine the expression levels of circulating CircHIPK3, CDR1as and their correlation with biochemical parameters in patients with T2DM, pre-diabetes and control subjects.

Methods and results

The expression of circRNAs in peripheral blood was determined using QRT-PCR in 70 patients with T2DM, 60 pre-diabetes and in 69 age and sex matched healthy controls. Moreover, bioinformatics tools were applied to explore and predict the potential interactions between circRNAs and other non-coding RNAs (ncRNAs). Our analysis revealed that the expression level of CircHIPK3 was significantly elevated in T2DM patients compared to healthy participants (P?<?0.001) and pre-diabetes subjects (P?=?0.018). In addition, ROC analysis suggested that at the cutoff value of 0.24 and the sensitivity and specificity of 50% and 88.4%, respectively, CircHIPK3 could distinguish between T2DM patients and control subjects. Furthermore, it was observed that the expression level of CDR1as is higher in pre-diabetic individuals than healthy individuals (P?=?0.004). Finally, Spearman correlation analysis showed that there was a significant correlation between CircHIPK3 and CDR1as expression levels and clinical and anthropometrical parameters such as BMI, systolic and diastolic blood pressure, HbA1c and fasting blood glucose (P?<?0.005).

Conclusions

The data of this study provided evidence that the expression levels of CircHIPK3, CDR1as increased in T2DM and pre-diabetes subjects, respectively.

     

Studies on serum gamma-glutamyl transpeptidase in primary idiopathic hypothyroidism patients.

Variations in the levels of serum gamma-glutamyl transpeptidase (GGT) were measured in control subjects and in 39 adult primary idiopathic hypothyroidism (PIH) patients. The serum GGT activity was low in PIH patients compared to that of control subjects. A more significant correlation was found between serum GGT and T3 (r = 0.766) but not with T4 (r = 0.476). The comparison of serum GGT with TSH has revealed that those two parameters are not parallel with each other (r = -0.454). No significant correlation between serum GGT activity, age, and sex in PIH patients and control subjects was observed. The present available data indicate that measurement of serum GGT might be useful as a marker index in PIH patients.     

On the origin of serum CD26 and its altered concentration in cancer patients

Dipeptidyl peptidase IV (DPP-IV), assigned to the CD26 cluster, is expressed on epithelial cells and lymphocytes and is a multifunctional or pleiotropic protein. Its peptidase activity causes degradation of many biologically active peptides, e.g. some incretins secreted by the enteroendocrine system. DPP-IV has, therefore, become a novel therapeutic target for inhibitors that extend endogenously produced insulin half-life in diabetics, and several reviews have appeared in recent months concerning the clinical significance of CD26/DPP-IV. Biological fluids contain relatively high levels of soluble CD26 (sCD26). The physiological role of sCD26 and its relation, if any, to CD26 functions, remain poorly understood because whether the process for CD26 secretion and/or shedding from cell membranes is regulated or not is not known. Liver epithelium and lymphocytes are often cited as the most likely source of sCD26. It is important to establish which tissue or organ is the protein source as well as the circumstances that can provoke an abnormal presence/absence or altered levels in many diseases including cancer, so that sCD26 can be validated as a clinical marker or a therapeutic target. For example, we have previously reported low levels of sCD26 in the blood of colorectal cancer patients, which indicated the potential usefulness of the protein as a biomarker for this cancer in early diagnosis, monitoring and prognosis. Through this review, we envisage a role for sCD26 and the alteration of normal peptidase capacity (in clipping enteroendocrine or other peptides) in the complex crosstalk between the lymphoid lineage and, at least, some malignant tumours.     

Homing Receptor Expression Is Deviated on CD56+ Blood Lymphocytes during Pregnancy in Type 1 Diabetic Women

Type 1 Diabetes Mellitus (T1DM) is characterized by an augmented pro-inflammatory immune state. This contributes to the increased risk for gestational complications observed in T1DM mothers. In normal pregnancies, critical immunological changes occur, including the massive recruitment of lymphocytes, particularly CD56^bright NK cells, into early decidua basalis and a 2^nd trimester shift towards Type 2 immunity. Decidual CD56^bright NK cells arise at least partly from circulating progenitors expressing adhesion molecules SELL and ITGA4 and the chemokine receptors CXCR3 and CXCR4. In vitro studies show that T1DM reduces interactions between blood CD56⁺ NK cells and decidual endothelial cells by reducing SELL and ITGA4-based interactions. To address the mechanisms by which specific lymphocyte subsets may be recruited from the circulation during pregnancy and whether these mechanisms are altered in T1DM, flow cytometry was used to examine eight peripheral blood lymphocyte subsets (Type 1 (IL18R1⁺) and Type 2 (IL1RL1⁺) CD56^bright NK, CD56^dim NK, NKT and T cells) from control and T1DM women. Blood was collected serially over pregnancy and postpartum, and lymphocytes were compared for expression of homing receptors SELL, ITGA4, CXCR3, and CXCR4. The decline of Type 1/Type 2 immune cells in normal pregnancy was driven by an increase in Type 2 cells that did not occur in T1DM. CD56^bright NK cells from control women had the highest expression of all four receptors with greatest expression in 2^nd trimester. At this time, these receptors were expressed at very low levels by CD56^bright NK cells from TIDM patients. Type 1/Type 2 NKT cell ratios were not influenced by either pregnancy or TIDM. Our results suggest that T1DM alters immunological balances during pregnancy with its greatest impact on CD56^bright NK cells. This implicates CD56^bright NK cells in diabetic pregnancy complications.     

血清γ-谷氨酰转肽酶水平与老年2型糖尿病患者并发急性冠脉综合征的相关性分析

目的:探讨血清γ-谷氨酰转肽酶(GGT)水平与老年2型糖尿病患者并发急性冠脉综合征的相关性。方法:选取2015年10月至2016年10月哈尔滨市第一医院收治的老年患者238例,根据病情分为单纯2型糖尿病组81例(DM组),单纯急性冠脉综合征组78例(ACS组),2型糖尿病患者合并急性冠脉综合征79例(DA组);选取同期来我院体检健康者83例作为对照组(NC组)。比较各组一般情况和血清学指标。结果:(1)DA组BMI大于NC组、DM组和ACS组,血清GGT、糖化血红蛋白(HbA1C)、低密度脂蛋白胆固醇(LDL-C)水平显著高于NC组、DM组和ACS组,血清总胆固醇(TC)、甘油三酯(TG)水平均高于NC组,高密度脂蛋白胆固醇(HDL-C)水平低于NC组(P0.05)。(2)血清GGT水平与TG、LDC-C水平呈正相关(p0.05)。结论:血清GGT水平升高是老年2型糖尿病患者并发急性冠脉综合征的独立危险因素,及时监测老年2型糖尿病患者GGT水平对预测急性冠脉综合征的发生具有重要意义。     

SUMO4基因多态性与2型糖尿病的关系

为了探讨北京汉族人群小泛素样修饰蛋白4(Small ubiquitin-like modifier 4, SUMO4)基因多态性与2型糖尿病(Type 2 diabetes mellitus, T2DM)的关系, 文章采用病例对照设计, 选取404例T2DM患者(T2DM组)以及年龄、性别匹配的500例健康对照者(Control组)作为研究对象, 应用聚合酶链反应-高分辨熔解曲线(PCR-HRM)技术结合测序验证法, 检测SUMO4基因3个单核苷酸多态性位点(rs237025、rs237024及rs600739)的基因型与等位基因分布情况, 比较T2DM组糖化血红蛋白(Hemoglobin A_1c, HbA_1c)在各基因型间的分布, 并进行单倍型分析。结果显示：①rs237025的G等位基因在T2DM组出现的频率更高(0.334 vs. 0.282, P =0.017); GA基因型携带者患T2DM的风险是AA基因型携带者的1.563倍(P=0.001; OR, 1.563; 95% CI, 1.189-2.053); 在显性模型(GG+GA vs. AA)分析中, G等位基因携带者(GG+GA)患T2DM的风险是AA基因型携带者的1.525倍(P =0.002; OR, 1.525; 95% CI, 1.169-1.989)。而rs237024和rs600739多态性未发现与T2DM的易感性相关(P >0.05)。②在T2DM组, rs237025的G等位基因携带者、rs237024的TT基因型携带者及rs600739的GG基因携带者具有较高的HbA_1c水平, 但各基因型携带者之间HbA_1c水平并无统计学差异(P >0.05)。③单倍型AAC、AGC及GGT与T2DM的易感性正相关(OR>1); 而单倍型AAT、GAC与T2DM的易感性负相关(OR<1)。据此得出结论：rs237025多态性与北京汉族人群T2DM的易感性相关, rs237024和rs600739多态性可能与T2DM的易感性不相关。     

SUMO4基因多态性与2型糖尿病的关系

为了探讨北京汉族人群小泛素样修饰蛋白4(Small ubiquitin-like modifier 4,SUMO4)基因多态性与2型糖尿病(Type 2 diabetes mellitus,T2DM)的关系,文章采用病例对照设计,选取404例T2DM患者(T2DM组)以及年龄、性别匹配的500例健康对照者(Control组)作为研究对象,应用聚合酶链反应-高分辨熔解曲线(PCR-HRM)技术结合测序验证法,检测SUMO4基因3个单核苷酸多态性位点(rs237025、rs237024及rs600739)的基因型与等位基因分布情况,比较T2DM组糖化血红蛋白(Hemoglobin A1c,HbA1c)在各基因型间的分布,并进行单倍型分析。结果显示:①rs237025的G等位基因在T2DM组出现的频率更高(0.334 vs.0.282,P=0.017);GA基因型携带者患T2DM的风险是AA基因型携带者的1.563倍(P=0.001;OR,1.563;95%CI,1.189-2.053);在显性模型(GG+GA vs.AA)分析中,G等位基因携带者(GG+GA)患T2DM的风险是AA基因型携带者的1.525倍(P=0.002;OR,1.525;95%CI,1.169-1.989)。而rs237024和rs600739多态性未发现与T2DM的易感性相关(P>0.05)。②在T2DM组,rs237025的G等位基因携带者、rs237024的TT基因型携带者及rs600739的GG基因携带者具有较高的HbA1c水平,但各基因型携带者之间HbA1c水平并无统计学差异(P>0.05)。③单倍型AAC、AGC及GGT与T2DM的易感性正相关(OR>1);而单倍型AAT、GAC与T2DM的易感性负相关(OR<1)。据此得出结论:rs237025多态性与北京汉族人群T2DM的易感性相关,rs237024和rs600739多态性可能与T2DM的易感性不相关。     

Evaluation of oxidative stress markers in pathogenesis of diabetic neuropathy

Experimental evidences suggest that hyperglycaemia-induced overproduction of reactive oxygen species and subsequent damage to proteins, lipids and DNA may play a key role in the development of distal symmetric polyneuropathy (DSPN)-the most common complication of diabetes mellitus. The study population consisted of 51 individuals aged 52-82 years classified into 3 groups: 16 patients diagnosed with type 2 diabetes mellitus (T2DM) with DSPN, 16 T2DM patients without DSPN and 19 control subjects without diabetes and neuropathy. The study was conducted to determine the activity of antioxidant enzymes: catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPX) and total antioxidant status (TAS) in the examined groups. An alkaline comet assay was used to determine the extent of DNA damage of oxidized purines as glicosylo-formamidoglicosylase (Fpg) sites, and oxidized pyrimidines as endonuclease III (Nth) sites. A significant decrease of SOD (P < 0.05), GPX (P < 0.05) and nonsignificant decrease of CAT (P > 0.05), and TAS status (P > 0.05) were seen in T2DM patients with neuropathy compared to T2DM patients as well as controls. T2DM patients with or without neuropathy revealed significantly lower (P < 0.05) plasma concentration of nitrous oxide compared to the control subjects. Endogenous level of oxidative DNA damage in T2DM patients with DSPN was significantly higher compared both to the controls and T2DM patients without DSPN (P < 0.001). Moreover, lymphocytes isolated from T2DM patients with DSPN were more susceptible to oxidative DNA lesions induced by hydrogen peroxide than from T2DM patients without DSPN (P < 0.001). Our results confirm hypothesis that oxidative stress may play a substantial role in the development and progression of diabetic distal symmetric polyneuropathy.     

Study of peripheral blood lymphocyte subset distribution and IL-2 receptor (IL-2 R) p55–p75 subunit expression in patients with cancer of different sites

The aim of the study was to evaluate the subset distribution and the IL-2 R p55–p75 subunit expression on unstimulated and phytohemagglutinin (PHA)-stimulated (at 3-d) peripheral blood mononuclear cells (PBMC), of patients with solid cancers of different sites. Indeed the expression of the two subunits of IL-2R is an essential prerequisite for The action of the IL-2 on CD8⁺, CD16⁺ lymphocytes as effectors in antitumor activity (LAK-cells). The subset distribution (CD3, CD4, CD8, CD16, DR) was assessed by cytofluorometry with specific monoclonal antibodies (MAbs); the p55 (CD25) and p75 subunit expression was evaluated by specific MAb (OKT26a and anti-p75). Ninety patients with advanced cancer (mainly non-small cell lung cancer [NSCLC], head and neck cancer, and gynecological cancer; mean age 55 yr; range 27–80) were studied. Thirty-five age- and sex-matched healthy subjects were studied as controls. Our data show that there is no significant difference in the subset distribution between cancer patients and controls. Furthermore, no difference has been found in the expression of p55 subunits on unstimulated PBMC between cancer patients and controls. No difference has been found in the expression of both p55 and p75 subunits on PHA-stimulated PBMC between cancer patients and controls. Our results can support the rationale for further clinical trials with IL-2 in solid malignancies.     

Modulation of Antigenic Phenotype in Cultured Human Osteoblast-like Cells by FGFb, TGFβ1, PDGF-BB, IL-2, IL-1β, LPS and IFNγ

Background/Aims Recent reports demonstrated that osteoblast-like cells can also exert activities directly associated with the immune system (cytokine synthesis, antigen presentation, phagocytosis and stimulation of T lymphocytes). The present study aimed to analyze the effect of Transforming growth factorβ1 (TGFβ1), Fibroblast growth factor basic (FGFb), Platelet-derived growth factor-BB (PDGF-BB), Interleukin-1β (IL-1β), Interleukin-2 (IL-2), Lipopolysaccharide (LPS) and Interferon-γ (IFNγ) on the expression on osteoblast-like cells of antigens involved in antigen presentation.Methods Flow cytometry was used to investigate whether the growth factors FGFb, TGFβ1, PDGF-BB, IL-2, IL-1β, LPS and IFNγ modulate the expression on cultured human osteoblast-like cells of different antigens involved in antigen-presentation and T cell activation.Results TGFβ1 treatment significantly reduced the expression of CD54 and CD86. IL-1β treatment significantly enhanced the expression of CD54, CD86 and HLA-DR. LPS and IFNγ treatments produced a major increase in CD54, CD80, CD86 and HLA-DR expression. Expression of these antigen-presenting molecules was not significantly modified by FGFb, PDGF-BB or IL-2 treatment.     

The HIV-1 gp120 inhibits the binding of adenosine deaminase to CD26 by a mechanism modulated by CD4 and CXCR4 expression

HIV-1 external envelope glycoprotein gp120 inhibits adenosine deaminase (ADA) binding to its cell surface receptor in lymphocytes, CD26, by a mechanism that does not require the gp120-CD4 interaction. To further characterize this mechanism, we studied ADA binding to murine clones stably expressing human CD26 and/or human CD4, and transiently expressing human CXCR4. In this heterologous model, we show that both recombinant gp120 and viral particles from the X4 HIV-1 isolate IIIB inhibited the binding of ADA to wild-type or catalytically inactive forms of CD26. In cells lacking human CXCR4 expression, this gp120-mediated inhibition of ADA binding to human CD26 was completely dependent on the expression of human CD4. In contrast, when cells were transfected with human CXCR4 the inhibitory effect of gp120 was significantly enhanced and was not blocked by anti-CD4 antibodies. These data suggest that the interaction of gp120 with CD4 or CXCR4 is required for efficient inhibition of ADA binding to CD26, although in the presence of CXCR4 the interaction of gp120 with CD4 may be dispensable.     

T cell activation by coxsackievirus B4 antigens in type 1 diabetes mellitus: evidence for selective TCR Vbeta usage without superantigenic activity.

Numerous clinical and epidemiological studies link enteroviruses such as the Coxsackie virus group with the autoimmune disease type 1 diabetes mellitus (DM). In addition, there are reports that patients with type 1 DM are characterized by skewing of TCR Vbeta chain selection among peripheral blood and intraislet T lymphocytes. To examine these issues, we analyzed TCR Vbeta chain-specific up-regulation of the early T cell activation marker, CD69, on CD4 T cells after incubation with Coxsackievirus B4 (CVB4) Ags. CD4 T cells bearing the Vbeta chains 2, 7, and 8 were the most frequently activated by CVB4. Up-regulation of CD69 by different TCR families was significantly more frequent in new onset type 1 DM patients (p = 0.04), 100% of whom (n = 8) showed activation of CD4 T cells bearing Vbeta8, compared with 50% of control subjects (n = 8; p = 0.04). T cell proliferation after incubation with CVB4 Ags required live, nonfixed APCs, suggesting that the selective expansion of CD4 T cells with particular Vbeta chains resulted from conventional antigen processing and presentation rather than superantigen activity. Heteroduplex analysis of TCR Vbeta chain usage after CVB4 stimulation indicated a relatively polyclonal, rather than oligo- or monoclonal response to viral Ags. These results provide evidence that new-onset patients with type 1 DM and healthy controls are primed against CVB4, and that CD4 T cell responses to the virus have a selective TCR Vbeta chain usage which is driven by viral Ags rather than a superantigen.     

Comodulation of CXCR4 and CD26 in human lymphocytes

We provide convergent and multiple evidence for a CD26/CXCR4 interaction. Thus, CD26 codistributes with CXCR4, and both coimmunoprecipitate from membranes of T (CD4(+)) and B (CD4(-)) cell lines. Upon induction with stromal cell-derived factor 1alpha (SDF-1alpha), CD26 is cointernalized with CXCR4. CXCR4-mediated down-regulation of CD26 is not induced by antagonists or human immunodeficiency virus (HIV)-1 gp120. SDF-1alpha-mediated down-regulation of CD26 is not blocked by pertussis toxin but does not occur in cells expressing mutant CXCR4 receptors unable to internalize. Codistribution and cointernalization also occurs in peripheral blood lymphocytes. Since CD26 is a cell surface endopeptidase that has the capacity to cleave SDF-1alpha, the CXCR4.CD26 complex is likely a functional unit in which CD26 may directly modulate SDF-1alpha-induced chemotaxis and antiviral capacity. CD26 anchors adenosine deaminase (ADA) to the lymphocyte cell surface, and this interaction is blocked by HIV-1 gp120. Here we demonstrate that gp120 interacts with CD26 and that gp120-mediated disruption of ADA/CD26 interaction is a consequence of a first interaction of gp120 with a domain different from the ADA binding site. SDF-1alpha and gp120 induce the appearance of pseudopodia in which CD26 and CXCR4 colocalize and in which ADA is not present. The physical association of CXCR4 and CD26, direct or part of a supramolecular structure, suggests a role on the function of the immune system and the pathophysiology of HIV infection.