CD26: a surface protease involved in T-cell activation

Clinical endocrinology and metabolism. Glucagon-like peptide-1 and glucagon-like peptide-2

The glucagon-like peptides (glucagon-like peptide-1 (GLP-1) and glucagon-like peptide-2 (GLP-2)) are released from enteroendocrine cells in response to nutrient ingestion. GLP-1 enhances glucose-stimulated insulin secretion and inhibits glucagon secretion, gastric emptying and feeding. GLP-1 also has proliferative, neogenic and antiapoptotic effects on pancreatic beta-cells. More recent studies illustrate a potential protective role for GLP-1 in the cardiovascular and central nervous systems. GLP-2 is an intestinal trophic peptide that stimulates cell proliferation and inhibits apoptosis in the intestinal crypt compartment. GLP-2 also regulates intestinal glucose transport, food intake and gastric acid secretion and emptying, and improves intestinal barrier function. Thus, GLP-1 and GLP-2 exhibit a diverse array of metabolic, proliferative and cytoprotective actions with important clinical implications for the treatment of diabetes and gastrointestinal disease, respectively. This review will highlight our current understanding of the biology of GLP-1 and GLP-2, with an emphasis on both well-characterized and more novel therapeutic applications of these peptides.

CD26/DPPIV and response to hepatitis B vaccination

The prevention of hepatitis B is important, since it is responsible for significant morbidity and mortality around the world. Unfortunately, hepatitis B vaccine does not always induce protective immunity. The lack of immune response to vaccine (non-responders) can depend on individual characteristics. The objective of this study was to correlate the CD26/DPPIV cellular expression and DPPIV serum activity with HBV vaccine response and its possible role as an indicator of immune competence acquisition. We also determined the cellular expression of CD3, CD19, CD56 and CD25 in peripheral blood T lymphocytes. Blood samples were obtained from 28 healthy human volunteers who were enrolled with a vaccination program. There were "responders" (RM = 13) and "non-responders" (NRM = 15), after vaccination. The lymphocyte populations were identified by flow cytometry. DPPIV serum activity was measured fluorimetrically. CD26 expression in responders (55.9 +/- 7.7%) versus in non-responders (51.9 +/- 7.0%) did not show a significant difference. The DPPIV serum activity in responders compared to in non-responder subgroup (59.9 +/- 8.4/50.3 +/- 10.6U/L) showed, however, a significant difference (P < 0.05). The expression of CD3, CD19 and CD56 on peripheral lymphocytes was similar between responders and non-responders. The expression of CD3CD26 (52.2 +/- 8.6%) and CD3CD25 (10.9 +/- 3.8%) in responders versus the expression of CD3CD26 (48.0 +/- 5.7%) and CD3CD25 (8 +/- 4.6%) in non-responders did not show statistically significant difference. CD25 referred as a marker of T lymphocyte activation was increased in responders (15.8 +/- 4.5%) versus in non-responders (10.1 +/- 4.8%), showing a significant difference (P = 0.003). It was, however, impossible to demonstrate an increase in CD3CD25 and CD3CD26 in the responder subgroup. This suggests that different lymphocyte subsets other than T cells are implicated in the response to hepatitis B vaccination.

Dipeptidyl peptidase IV in tumor progression

Dipeptidyl peptidase IV (DPPIV) is a 110-kDa glycoprotein with ubiquitous expression. Several recent studies have shown that DPPIV affects tumor progression in several human malignancies. We found that ovarian carcinoma cell lines with higher DPPIV expression showed less invasive potential. Furthermore, introduction of DPPIV cDNA into SKOV3 cells (SKDPIV), derived from serous cystadenocarcinoma showing little DPPIV expression, caused a significant decrease in both migration and invasive potential. In addition, nude mice inoculated with SKDPIV cells showed significantly less peritoneal dissemination and longer survival time than those inoculated with parental or vector-transfected cells. We further examined the mechanisms of anti-invasive ability of DPPIV. The expression of E-cadherin was positively correlated with DPPIV expression among five independent ovarian carcinoma cell lines. The SKDPIV cells showed enhanced expression of E-cadherin with a cellular morphological change from a fibroblastic and motile phenotype to an epithelial phenotype compared to parental and MOCK cells. In addition, matrix metalloproteinase 2 (MMP-2) and membrane type 1 matrix metalloprotease (MT1-MMP), which are important markers associated with invasive and metastatic potential, were remarkably reduced in SKDPIV cells. In contrast, tissue inhibitors of matrix metalloproteinases (TIMPs) were enhanced by DPPIV transfection. These findings imply that DPPIV may functionally suppress peritoneal dissemination and progression of ovarian carcinoma by regulating the expression levels of several molecules associated with carcinoma cell invasion and progression.

CD26 up-regulates expression of CD86 on antigen-presenting cells by means of caveolin-1

CD26 is a T cell costimulatory molecule with dipeptidyl peptidase IV activity in its extracellular region. We previously reported that recombinant soluble CD26 enhanced T cell proliferation induced by the recall antigen tetanus toxoid (TT). However, the mechanism involved in this enhancement is not yet elucidated. We now demonstrate that CD26 binds Caveolin-1 on antigen-presenting cells, and that residues 201-211 of CD26 along with the serine catalytic site at residue 630 contribute to binding to caveolin-1 scaffolding domain. In addition, after CD26-caveolin-1 interaction on TT-loaded monocytes, caveolin-1 is phosphorylated, which links to activate NF-kappaB, followed by up-regulation of CD86. Finally, reduced caveolin-1 expression on monocytes inhibits CD26-mediated CD86 up-regulation and abrogates CD26 effect on TT-induced T cell proliferation. Taken together, these results strongly suggest that CD26-caveolin-1 interaction plays a role in the up-regulation of CD86 on TT-loaded monocytes and subsequent engagement with CD28 on T cells, leading to antigen-specific T cell activation.

Therapeutic strategies based on glucagon-like peptide 1

Glucagon-like peptide (GLP)-1 is an incretin hormone with potent glucose-dependent insulinotropic and glucagonostatic actions, trophic effects on the pancreatic beta-cells, and inhibitory effects on gastrointestinal secretion and motility, which combine to lower plasma glucose and reduce glycemic excursions. Furthermore, via its ability to enhance satiety, GLP-1 reduces food intake, thereby limiting weight gain, and may even cause weight loss. Taken together, these actions give GLP-1 a unique profile, considered highly desirable for an antidiabetic agent, particularly since the glucose dependency of its antihyperglycemic effects should minimize any risk of severe hypoglycemia. However, its pharmacokinetic/pharmacodynamic profile is such that native GLP-1 is not therapeutically useful. Thus, while GLP-1 is most effective when administered continuously, single subcutaneous injections have short-lasting effects. GLP-1 is highly susceptible to enzymatic degradation in vivo, and cleavage by dipeptidyl peptidase IV (DPP-IV) is probably the most relevant, since this occurs rapidly and generates a noninsulinotropic metabolite. Strategies for harnessing GLP-1's therapeutic potential, based on an understanding of factors influencing its metabolic stability and pharmacokinetic/pharmacodynamic profile, have therefore been the focus of intense research in both academia and the pharmaceutical industry. Such strategies include DPP-IV-resistant GLP-1 analogs and selective enzyme inhibitors to prevent in vivo degradation of the peptide.

CD30 Is Involved in Inhibition of T-Cell Proliferation by Hodgkin’s Reed-Sternberg Cells 1

CD30 is expressed on Hodgkin's Reed-Sternberg (H-RS) cells, the tumor cells in Hodgkin's disease. Increased levels of serum CD30 are observed in Hodgkin's disease patients and are a good marker for predicting a poor prognosis and a poor response to therapy. In this study, we addressed the effect of CD30 on T cells. We showed that CD30, either as a membranous protein on H-RS cells and Chinese hamster ovary cells or as a plate-bound chimeric protein, inhibited T-cell proliferation. Anti-CD3-stimulated T cells in the presence of CD30 failed to increase tritium uptake and failed to express CD25 and CD26 and to produce interleukin 2. The inhibition of T-cell proliferation was, however, reversed with addition of exogenous interleukin 2 or pretreatment of H-RS cells with anti-CD30. Inability of T cells to express CD25 and CD26 in cocultures with H-RS cells or a plate-bound CD30 chimeric protein is in accordance with the results of immunohistochemistry on disease-involved tissues. We conclude that H-RS cells are able to inhibit the proliferation and activation of T cells through CD30-related interaction. The outcome of CD30-related interaction is an ineffective antitumor immunity, which is clearly in favor of the growth and survival of the tumor cells.

3D structure of the CD26-ADA complex obtained by cryo-EM and single particle analysis

The specific binding of adenosine deaminase to the multifunctional membrane glycoprotein dipeptidyl peptidase IV is thought to be immunologically relevant for certain regulatory and co-stimulatory processes. In this study we present the 3D structure of the complete CD26-ADA complex obtained by single particle cryo-EM at 22A resolution. ADA binding occurs at the outer edges of the beta-propeller of CD26. Docking calculations of available CD26 and ADA crystal data into the obtained EM density map revealed that the ADA-binding site is stretched across CD26 beta-propeller blades 4 and 5 involving the outermost distal hydrophobic amino acids L294 and V341 but not T440 and K441 as suggested by antibody binding. Though the docking of the ADA orientation appears less significant due to the lack of distinct surface features, non-ambiguous conclusions can be drawn in the combination with earlier indirect non-imaging methods affirming the crucial role of the ADA alpha2-helix for binding.

Adenosine deaminase 2 from chicken liver: purification, characterization, and N-terminal amino acid sequence

Adenosine deaminase (ADA) is involved in purine metabolism and plays an important role in the mechanism of the immune system. ADA activity is composed of two kinetically distinct isozymes, which are referred to as ADA1 and ADA2. ADA1 is widely distributed in many animals and well characterized. On the contrary, relatively little is known about ADA2. In this study, we first purified ADA2 to homogeneity from chicken liver. The purified enzyme had a molecular mass of approximately 110 kDa on gel filtration. Also, the enzyme was shown to be a homodimer with an estimated molecular mass of 61 kDa on SDS-PAGE. Following treatment with N-glycosidase, the molecular mass of ADA2 changed to 55 kDa. Several properties of the highly purified ADA2 were also investigated in this study. Furthermore, the N-terminal amino acid sequence of ADA2 was determined.

Neuropeptide Y (NPY) suppresses experimental autoimmune encephalomyelitis: NPY1 receptor-specific inhibition of autoreactive Th1 responses in vivo

Prior studies have revealed that the sympathetic nervous system regulates the clinical and pathological manifestations of experimental autoimmune encephalomyelitis (EAE), an autoimmune disease model mediated by Th1 T cells. Although the regulatory role of catecholamines has been indicated in the previous works, it remained possible that other sympathetic neurotransmitters like neuropeptide Y (NPY) may also be involved in the regulation of EAE. Here we examined the effect of NPY and NPY receptor subtype-specific compounds on EAE, actively induced with myelin oligodendrocyte glycoprotein 35-55 in C57BL/6 mice. Our results revealed that exogenous NPY as well as NPY Y(1) receptor agonists significantly inhibited the induction of EAE, whereas a Y(5) receptor agonist or a combined treatment of NPY with a Y(1) receptor antagonist did not inhibit signs of EAE. These results indicate that the suppression of EAE by NPY is mediated via Y(1) receptors. Furthermore, treatment with the Y(1) receptor antagonist induced a significantly earlier onset of EAE, indicating a protective role of endogenous NPY in the induction phase of EAE. We also revealed a significant inhibition of myelin oligodendrocyte glycoprotein 35-55-specific Th1 response as well as a Th2 bias of the autoimmune T cells in mice treated with the Y(1) receptor agonist. Ex vivo analysis further demonstrated that autoimmune T cells are directly affected by NPY via Y(1) receptors. Taken together, we conclude that NPY is a potent immunomodulator involved in the regulation of the Th1-mediated autoimmune disease EAE.

A role for interleukin-12 in the regulation of T cell plasma membrane compartmentation

The immunological synapse initiates the clustering and stabilization of the T cell receptor by the formation of a large lipid microdomain that accumulates (e.g. CD4/CD8) and segregates (e.g. CD45 and LFA-1) some proteins of the T cell plasma membrane. This work shows that a fraction of transmembrane glycoproteins CD26 and CD45 (the R0 isoform in particular) is present in the rafts of fresh and activated human T lymphocytes. CD26 is proposed as the costimulator of TCR-dependent activation, and CD45 is essential to the T cell activation process because it dephosphorylates at least the inhibitory site of Src kinases. These findings support a more complex model of compartmentation, depending on the stage of T cell maturation and post-transcriptional and post-translational regulation. In addition, interleukin 12 (IL-12; inducer of TH1 responses) drives CD26 and CD45R0 to particular microdomains, thereby involving interleukins in the rules governing raft inclusion or exclusion. The physical association of CD26 and CD45R0 has long been reported. The results presented in this work fit a model in which IL-12 up-regulates a certain type of CD26 expression that interacts on the cell surface with CD45R0, near but outside of the raft core. The use of antisense oligonucleotides for the CD26 mRNAs demonstrated that both events (enhanced by IL-12), CD26-CD45R0 association and membrane compartment redistribution, are related. Thus, CD26 could be part of a shuttling mechanism for CD45 that regulates membrane tyrosine-phosphatase activities, e.g. to control IL-12 receptor-dependent signal transduction.

A novel consensus motif in fibronectin mediates dipeptidyl peptidase IV adhesion and metastasis

Lung endothelial dipeptidyl peptidase IV (DPPIV/CD26) is a vascular address for cancer cells decorated with cell-surface polymeric fibronectin (poly-FN). Here, we identified the DPPIV-binding sites in FN and examined the effect of binding site peptides on DPPIV/poly-FN adhesion and metastasis. Using proteolytic fragments and maltose-binding protein fusion proteins that together span full-length FN, we found DPPIV-binding sites in type III repeats 13, 14, and 15 (FNIII13, -14, and -15, respectively). DPPIV binding was mediated by the consensus motif T(I/L)TGLX(P/R)G(T/V)X and was confirmed by swapping this motif in FNIII13, -14, and -15 with the corresponding region in FNIII12, which did not bind DPPIV. DPPIV binding was lost in swapped FNIII13, -14, and -15 and gained in swapped FNIII12 (FNIII12(14)). Peptides containing the DPPIV-binding domain of FNIII14 blocked DPPIV/poly-FN adhesion and impeded pulmonary metastasis. This study adds to the classes of cell-surface adhesion receptors for FN and will help in the further characterization of the functional implications of the DPPIV/poly-FN adhesion in metastasis and possibly in cell-mediated immunity involving DPPIV-expressing lymphocytes.

Dipeptidyl-peptidase IV from bench to bedside: an update on structural properties, functions, and clinical aspects of the enzyme DPP IV

Dipeptidyl-peptidase IV/CD26 (DPP IV) is a cell-surface protease belonging to the prolyloligopeptidase family. It selectively removes the N-terminal dipeptide from peptides with proline or alanine in the second position. Apart from its catalytic activity, it interacts with several proteins, for instance, adenosine deaminase, the HIV gp120 protein, fibronectin, collagen, the chemokine receptor CXCR4, and the tyrosine phosphatase CD45. DPP IV is expressed on a specific set of T lymphocytes, where it is up-regulated after activation. It is also expressed in a variety of tissues, primarily on endothelial and epithelial cells. A soluble form is present in plasma and other body fluids. DPP IV has been proposed as a diagnostic or prognostic marker for various tumors, hematological malignancies, immunological, inflammatory, psychoneuroendocrine disorders, and viral infections. DPP IV truncates many bioactive peptides of medical importance. It plays a role in glucose homeostasis through proteolytic inactivation of the incretins. DPP IV inhibitors improve glucose tolerance and pancreatic islet cell function in animal models of type 2 diabetes and in diabetic patients. The role of DPP IV/ CD26 within the immune system is a combination of its exopeptidase activity and its interactions with different molecules. This enables DPP IV/CD26 to serve as a co-stimulatory molecule to influence T cell activity and to modulate chemotaxis. DPP IV is also implicated in HIV-1 entry, malignant transformation, and tumor invasion.

Dipeptidyl peptidase IV (DPPIV) enzyme activity on immature T-cell line R1.1 is down-regulated by dynorphin-A(1-17) as a non-substrate inhibitor

In this study we examined surface expression of CD26 and the corresponding enzyme activity of dipeptidyl peptidase IV (DPPIV) on the cells of immature murine T-cell line, R1.1. The data obtained have shown that R1.1 cells express high density of surface CD26 as compared to normal thymus cells. This was associated with strong enzyme activity, which, based on substrates and inhibitor specificity, corresponded to DPPIV. The DPPIV enzyme activity of R1.1 cells was 10 times stronger than that found on normal murine thymus cells (V(max) = 39 micromol/min/10(6) cells, vs 3.7 micromol/min/10(6) cells, respectively). Upon activation with anti-CD3, up-regulation of both membrane CD26, as well as of DPPIV enzyme activity on R1.1 cells were observed. The finding of strong DPPIV on R1.1 cells makes them suitable model for testing putative substrates/inhibitors of the enzyme in its natural microenvironment. Since in addition to strong DPPIV, R1.1 cells also express kappa opioid receptors (KOR) [European Journal of Pharmacology 227 (1992) 257], we tested the effect of dynorphin-A(1-17), an endogenous opioid peptide with KOR selectivity, on DPPIV of R1.1 cells. Dynorphin-A(1-17) down-regulated DPPIV in a dose-dependent manner, with the potency similar to that of substance P, a known natural DPPIV substrate [Journal of Pharmacology and Experimental Therapeutics 260 (1992) 1257]. DPPIV down-regulation was resistant to bestatin and thiorphan, the inhibitors of two cell surface peptidases (APN and NEP, respectively) with potential of dynorphin-A(1-17) degradation, suggesting that the mechanism underlying the observed effect does not involve degradative products of dynorphin-A(1-17). DPPIV down-regulation was also resistent to KOR antagonist, NBI, suggesting that the mechanism underlying the observed phenomenon involves neither cointernalization of KOR and DPPIV. Collectively, cells of immature T cell line, R1.1 exert strong DPPIV enzyme activity, which could be down-regulated in the presence of dynorphin-A(1-17) by mechanism that presumably includes non-substrate inhibition. By down-regulating DPPIV, dynorphin-A(1-17) may indirectly affect activity and/or specificity of natural substrates of DPPIV, such as substance P, RANTES, and endomorphins.

Similar increased serum dipeptidyl peptidase IV activity in chronic hepatitis C and other viral infections

BACKGROUND

Dipeptidyl peptidase IV is a transmembrane enzyme widely expressed in many cell types, but also present as a soluble form in biological fluids. Its abnormal activity is sometimes associated with liver disease related pathologies.

OBJECTIVES

The aim of this study was to evaluate the clinical relevance of changes in serum DPPIV activity in hepatitis C and other viral infections.

STUDY DESIGN

DPPIV activity was assessed by using a microplate-based colorimetric assay on serum from 88 subjects: 12 healthy uninfected controls, 10 patients with primary biliary cirrhosis (PBC) as a reference group, 36 HCV-infected patients, and patients suffering from viral infections of different etiologies. Levels of DPPIV activity were compared with: (1) those of other serum biochemical parameters such as alanine aminotransferase (ALT), aspartate aminotransferase (AST) and gamma glutamyl transpeptidase (GGT), and bilirubin concentrations; and (2) criteria representative of liver histological status.

RESULTS

Compared with healthy subjects, DPPIV activity was significantly increased during viral infections and in PBC (P<0.01). In HCV-infected patients, the median activity (interquartile range, IQR), 29.78 IU/l (24.66-35.95), differed significantly (P<0.05) from that of controls: 21.42 (19.76-24.93). No correlation was observed between DPPIV activity and either ALT, AST, bilirubin, or the stage of liver fibrosis and necroinflammatory activity, although GGT was moderately correlated (r=0.58, P<0.05).

CONCLUSIONS

Although we confirmed an elevation of serum DPPIV activity in PBC, it seems to be a non-specific phenomenon common to viral infections. The absence of correlation between serum DPPIV and markers of liver disease in HCV-infected patients, suggests that this activity originates not only from the liver, but also from other sources such as peripheral blood cells involved in the control of viral infections.

Increased expression of T cell activation markers (CD25, CD26, CD40L and CD69) in atherectomy specimens of patients with unstable angina and acute myocardial infarction

Atherosclerotic plaques contain a chronic immune mediated inflammation in which T cells play an important role. A previous study revealed that the numbers of interleukin-2 receptor-positive T cells is increased in culprit lesions of patients with acute coronary syndromes; a finding of considerable interest since it indicates a recent change in the intraplaque T cell mediated immune response. Confirmation of this observation is important, because it could provide insight into the onset of the acute event. We have, therefore, expanded our earlier work by using a panel of different T cell activation markers (CD25, CD26, CD40L, CD69). The study is based on 58 culprit lesions from patients who underwent coronary atherectomy. There were four groups of patients: chronic stable angina (n=13), stabilized unstable angina (n=16), refractory unstable angina (n=15), and acute myocardial infarction (AMI; n=14). Activated T cells were expressed as a percentage of the total of CD3-positive cells. CD25, CD26, CD40L, and CD69/CD3 percentages increased with the severity of the coronary syndrome. In patients with AMI all percentages were significantly higher than in patients with chronic stable angina. CD25, CD26, CD40L, and CD69/CD3 percentages in patients with an unstable condition (refractory unstable angina and AMI) were significantly higher than those in patients with a stable condition (chronic stable or stabilized unstable angina) The finding that the percentage of T cells with recent onset activation is significantly increased in the culprit lesions of patients with acute coronary syndromes suggests strongly that a recent change in pathogenic stimulation has occurred leading to local T cell activation.

The crystal structure of dipeptidyl peptidase IV (CD26) reveals its functional regulation and enzymatic mechanism

The membrane-bound glycoprotein dipeptidyl peptidase IV (DP IV, CD26) is a unique multifunctional protein, acting as receptor, binding and proteolytic molecule. We have determined the sequence and 1.8 A crystal structure of native DP IV prepared from porcine kidney. The crystal structure reveals a 2-2-2 symmetric tetrameric assembly which depends on the natively glycosylated beta-propeller blade IV. The crystal structure indicates that tetramerization of DP IV is a key mechanism to regulate its interaction with other components. Each subunit comprises two structural domains, the N-terminal eight-bladed beta-propeller with open Velcro topology and the C-terminal alpha/beta-hydrolase domain. Analogy with the structurally related POP and tricorn protease suggests that substrates access the buried active site through the beta-propeller tunnel while products leave the active site through a separate side exit. A dipeptide mimicking inhibitor complexed to the active site discloses key determinants for substrate recognition, including a Glu-Glu motif that distinguishes DP IV as an aminopeptidase and an oxyanion trap that binds and activates the P(2)-carbonyl oxygen necessary for efficient postproline cleavage. We discuss active and nonactive site-directed inhibition strategies of this pharmaceutical target protein.

Dipeptidyl peptidase IV expression in thyroid cytology: retrospective histologically confirmed study

Fine needle aspiration cytology (FNAC) of the thyroid gland is a well-established method. However, it has inherent limitations, especially in the diagnosis of follicular and oncocytic tumours and in distinguishing between nuclear atypia in colloid goitre with regressive changes and cystic papillary carcinoma. The aim of our study was to evaluate dipeptidyl peptidase IV (DPP IV) as a marker of malignancy in FNAC. We tested 254 thyroid specimens (intraoperative imprint smears) for DPP IV. The sensitivity was 71%, the specificity was 96%, and the diagnostic accuracy was 93%, respectively, with a threshold of 50% of positive cells. To the best of our knowledge it is the largest histologically confirmed study reported in the literature. We suggest the assessment of DPP IV as an adjunct diagnostic marker of malignancy in thyroid specimens suspicious of papillary carcinoma. However, the value of the marker in follicular lesions is very limited.

Chemokines, cytokines and their receptors in Hodgkin's lymphoma cell lines and tissues

BACKGROUND

Hodgkin's lymphoma (HL) is characterized by a minority of neoplastic cells, the so-called Reed-Sternberg (RS) cells, and an admixture of reactive cells including lymphocytes, plasma cells, eosinophils and histiocytes. Cytokines produced in HL, either by RS or infiltrating cells, might explain the presence and maintenance of an impaired immune response. Chemokines (cytokines with chemoattractant properties) produced by RS cells play a major role in leukocyte trafficking. These molecules with specific receptor affinities contribute, for example by attracting TH2-like T cells, to the maintenance of a favorable environment for survival of RS cells.

RESULTS AND DISCUSSION

Cross-talk between RS cells and reactive elements involves several cytokine/chemokines that process proliferative [interleukin (IL)-13 and IL-17], immunosuppressive (IL-10 and transforming growth factor-beta) and background formation (IL-5, TARC, MDC, IP-10, RANTES, Mig and others) messages. These autocrine and paracrine interactions lead to an environment where RS cells are able to proliferate, escape from apoptosis and survive host anti-tumor defense.

CONCLUSIONS

The proper modulation of these complex pathways may allow the development of new strategies in HL therapy.

Increased expression of dipeptidyl peptidase IV in human mesothelial cells by malignant ascites from ovarian carcinoma patients

Cell surface aminopeptidases play an important role in biological processes through degradation of small peptides. There are many bioactive peptides in ascites and these peptides are involved in carcinoma cell dissemination and infiltration. In human mesothelial cells dipeptidyl peptidase IV (DPPIV) shows the highest expression mostly in four cell surface aminopeptidases: aminopeptidase A, neutral endopeptidase 24-11, aminopeptidase N and DPPIV. Since mesothelial cells are always in contact with ascites, we examined the influence of malignant ascites on DPPIV. DPPIV enzyme activity in mesothelial cells was enhanced by the addition of ascites obtained from ovarian carcinoma patients in a time- and concentration-dependent manner, and flow cytometry and immunocytochemistry also revealed an increased expression of DPPIV on the cell surface of mesothelial cells. The <3-kD fraction of malignant ascites increased the DPPIV enzyme activity to the same level as the total ascites. Northern hybridization demonstrated that DPPIV mRNA was increased 3-fold by the addition of the <3-kD malignant ascites. In conclusion, DPPIV is highly expressed in human mesothelial cells and was regulated by ascites.

Streptokinase promotes development of dipeptidyl peptidase IV (CD26) autoantibodies after fibrinolytic therapy in myocardial infarction patients

Dipeptidyl peptidase IV (DPP IV) (CD26) plays a critical role in the modulation and expression of autoimmune and inflammatory diseases. We recently reported that sera from patients with rheumatoid arthritis and systemic lupus erythematosus contained low levels of DPP IV and high titers of anti-DPP IV autoantibodies of the immunoglobulin A (IgA) and IgG classes and found a correlation between the low circulating levels of DPP IV and the high titers of anti-DPP IV autoantibodies of the IgA class. Since streptokinase (SK) is a potent immunogen and binds to DPP IV, we speculated that patients with autoimmune diseases showed higher DPP IV autoantibody levels than healthy controls as a consequence of an abnormal immune stimulation triggered by SK released during streptococcal infections. We assessed this hypothesis in a group of patients suffering from acute myocardial infarction, without a chronic autoimmune disease, who received SK as part of therapeutic thrombolysis. Concomitant with the appearance of anti-SK antibodies, these patients developed anti-DPP IV autoantibodies. These autoantibodies bind to DPP IV in the region which is also recognized by SK, suggesting that an SK-induced immune response is responsible for the appearance of DPP IV autoantibodies. Furthermore, we determined a correlation between high titers of DPP IV autoantibodies and an augmented clearance of the enzyme from the circulation. Serum levels of the inflammatory cytokines tumor necrosis factor alpha (TNF-alpha) and interleukin 6 (IL-6) increased significantly after 30 days of SK administration, while the levels of soluble IL-2 receptor remained unchanged during the same period, suggesting a correlation between the lower levels of circulating DPP IV and higher levels of TNF-alpha and IL-6 in serum in these patients.

Characterization and purification of adenosine deaminase 1 from human and chicken liver

Adenosine deaminase 1 (ADA1) was purified from human and chicken liver. The purified enzyme had a molecular weight of approximately 42,000 Da on SDS-PAGE. In humans, ADA1 was mainly purified concomitant with ADA-binding protein, dipeptidyl peptidase IV (DPP IV)/CD26; however, in chickens, only ADA1 without DPP IV was purified. Both human and chicken ADA1s showed similar properties on substrate specificities, sensitivities on inhibitors, and pH profile. However, they had different affinities with adenosine-Sepharose and IgG anti-ADA1-Sepharose. Human ADA1 was not adsorbed in adenosine-Sepharose column, but chicken ADA1 was adsorbed. As for IgG anti-ADA1-Sepharose column, the results were converse. Furthermore, human ADA1 could bind to DPP IV whereas chicken ADA1 could not.

Expression of T lymphocyte chemoattractants and activation markers in vernal keratoconjunctivitis

BACKGROUND/AIMS

T lymphocytes are present in increased numbers in the conjunctiva of patients with vernal keratoconjunctivitis (VKC) and their activation has a central role in the pathogenesis of the chronic allergic inflammatory reactions seen in VKC. The aims of this study were to examine the expression of three recently described potent T lymphocyte chemoattractants, PARC (pulmonary and activation regulated chemokine), macrophage derived chemokine (MDC), and I-309, the MDC receptor CCR4, and T lymphocyte activation markers, CD25, CD26, CD62L, CD71, and CD30, and to correlate them with the counts of CD3(+) T lymphocytes in the conjunctiva of patients with VKC.

METHOD

Conjunctival biopsy specimens from 11 patients with active VKC, and eight control subjects were studied by immunohistochemical techniques using a panel of monoclonal and polyclonal antibodies directed against PARC, MDC, I-309, CCR4, CD25, CD26, CD62L, CD71, and CD30. The numbers of positively stained cells were counted. The phenotype of inflammatory cells expressing chemokines was examined by double immunohistochemistry.

RESULTS

In the normal conjunctiva, vascular endothelial cells in the upper substantia propria showed weak immunoreactivity for CD26. There was no immunoreactivity for the other antibodies. VKC specimens showed inflammatory cells expressing PARC, MDC, and I-309. The numbers of PARC(+) inflammatory cells were higher than the numbers of MDC(+) and I-309(+) inflammatory cells and the mean values of the three groups differed significantly (17.0 (SD 10.1); 9.5 (9.9), and 4.3 (7.9), respectively, p = 0.0117, ANOVA). The numbers of PARC(+) inflammatory cells had the strongest correlation with the numbers of CD3(+) T lymphocytes. Few CCR4(+) inflammatory cells were observed in only three specimens. Double immunohistochemistry revealed that all inflammatory cells expressing chemokines were CD68(+) monocytes/macrophages. The numbers of CD25(+) T lymphocytes were higher than the numbers of CD26(+), CD62L(+), CD71(+), and CD30(+) T lymphocytes and the mean values of the five groups differed significantly (46.2 (27.9), 30.7 (16.0), 20.1 (8.6), 7.8 (7.7), and 6.5 (4.0), respectively, p <0.001, ANOVA). The numbers of CD25(+) T lymphocytes had the strongest correlation with the numbers of CD3(+) T lymphocytes.

CONCLUSION

These results suggest a potential role for PARC, MDC, and I-309 in attracting T lymphocytes into conjunctiva in VKC. T lymphocytes in VKC are activated and express several activation markers which might contribute to the pathogenesis of VKC.

Human CD26 expression in transgenic mice affects murine T-cell populations and modifies their subset distribution

CD26 is a type II transmembrane glycoprotein with dipeptidyl peptidase (DPPIV) activity, constitutively expressed in different cell types and contributing to T-cell activation by acting as costimulatory molecule. Although data suggest an important role for CD26 within the immune system, the physiologic function of this molecule is still unknown. To investigate the role of CD26 in vivo we have produced transgenic mice expressing the human molecule in T cells. Human CD26 (huCD26) is constitutively expressed in all thymocytes and peripheral T lymphocytes of these transgenic mice and is endowed with an enhanced DPPIV activity. CD26 transgene expression induces major phenotypic changes to T-cell populations within the thymus and in peripheral blood. After the onset of sexual maturity, huCD26 expression induces an age-related overreduction of thymus cellularity accompanied by a relative impairment of thymocyte proliferation following lectin stimulation. Also the peripheral blood T-cell pool is reduced in huCD26 transgenic mice and this is accompanied by an increase of the apoptotic rate of CD4+ and CD8+ subpopulations. Taken together these data suggest that CD26 interferes with transduction pathway(s) needed for the maturation of T cells and plays an important role in T lymphocyte homeostasis in peripheral blood.

Characterization of a monoclonal antibody specific for a novel primate cell surface marker with distinct biochemical properties on human erythroleukemia and myeloid cell lines

A hybridoma, CSC-1, which secretes monoclonal antibody (MAb) specific for a cell surface molecule on African green monkey kidney cell line, BGMK, was isolated and characterized. The cell surface molecule recognized by CSC-1 is widely expressed on a variety of human cell lines. Among the hematopoietic cell lines examined, the CSC-1 marker seems to be preferentially expressed by lymphoid cell lines (e.g., Raji, CEM-SS, Jurkat, and MOLT-3). Although CSC-1 also recognizes some uncommitted myeloid and erythroleukemia cell lines (e.g., U-937 and K562), the CSC-1 marker expression on these cell lines is subjected to PMA-induced down-regulation. In addition, the PMA-induced cell surface down-regulation of the CSC-1 marker required more than 24 h. Proteolytic analysis shows that the CSC-1 marker can be categorized into proteinase K-resistant and-sensitive phenotypes. Furthermore, the CSC-1 marker exhibits a slow cell surface turnover rate after proteinase K treatment. Our data suggest that the CSC-1 cell surface molecule might be useful as a megakaryocytic or monocytic differentiation marker.

Immune activation and induction of HIV-1 replication within CD14 macrophages during acute Plasmodium falciparum malaria coinfection

OBJECTIVES

To determine the impact of Plasmodium falciparum malaria coinfection and its treatment on cellular reservoirs of viral replication in HIV-1-infected persons and to relate this to changes in systemic immune activation.

METHODS

Plasma samples were obtained from HIV-1-infected individuals (n = 10) at diagnosis of acute malaria, 4 weeks after parasite clearance and from HIV-infected aparasitemic controls (n = 10). Immunomagnetic HIV-1 capture analysis was used to determine the cellular origin of cell-free virus particles present in all 30 plasma samples and indices of immune activation were measured using enzyme-linked immunosorbent assays.

RESULTS

Compared with controls, the detectable proportion of HIV-1 particles derived from CD14 macrophages and CD26 lymphocytes was increased in persons with acute malaria coinfection and correlated with markedly increased plasma concentrations of both proinflammatory cytokines and soluble markers of macrophage and lymphocyte activation. Parasite clearance following treatment with antimalarial drugs resulted in decreased detection of HIV-1 particles derived from the CD14 macrophage cell subset and correlated with a marked diminution in systemic immune activation.

CONCLUSIONS

Acute P. falciparum malaria coinfection impacts virus-host dynamics in HIV-1-infected persons at the cellular level, notably showing a reversible induction of HIV-1 replication in CD14 macrophages that is associated with changes in immune activation.

The role of dipeptidyl peptidase IV (DP IV) enzymatic activity in T cell activation and autoimmunity

Activated T lymphocytes express high levels of dipeptidyl peptidase IV (DP IV)/CD26. Recent studies support the notion that DP IV may play an important role in the regulation of differentiation and growth of T lymphocytes. This article gives a short overview on DP IV/CD26 expression and effects on immune cells in vitro and in vivo. A major focus of this review are clinical aspects of the function of CD26 on hematopoietic cells and the potential usage of synthetic DP IV inhibitors as therapeutics in inflammatory disorders.

Loss of dipeptidylpeptidase IV activity in chronic rhinosinusitis contributes to the neurogenic inflammation induced by substance P in the nasal mucosa

In this study, we have found that dipeptidylpeptidase IV (DPPIV) plays in vivo an active role in the modulation of the inflammatory response of chronic rhinosinusitis. Human nasal mucosa expresses DPPIV-like immunoreactivity in submucosal seromucus glands, leukocytes, and endothelial cells of blood vessels. DPPIV enzymatic activity in nasal tissue biopsies taken from patients suffering from chronic rhinosinusitis was correlated inversely with the density of inflammatory cells in the nasal mucosa, and the DPPIV activity rose when chronic rhinosinusitis was treated. By using a pig animal model, we have shown that the intranasal administration of recombinant DPPIV decreased the vasodilatation induced by exogenous substance P (SP), a proinflammatory peptide released by sensory nerves. In contrast, an inhibitor of DPPIV enhanced the vasodilatatory effect at low doses of SP. SP5-11 was 100- to 1000-fold less potent than SP as a vasodilator of the nasal mucosa. The vasodilatatory effect of SP was abolished by a NK1 receptor antagonist. In conclusion, these results suggest a new pathophysiological pathway for rhinitis based on clinical observations in humans, indicating the involvement of an enzyme to modulate non-adrenergic and non-cholinergic substrate that occurred during nasal dysfunctions.

Common and differential chemokine expression patterns in rs cells of NLP, EBV positive and negative classical Hodgkin lymphomas

Hodgkin lymphoma (HL) is characterized by a minority of neoplastic cells, the so-called Reed-Sternberg (RS) cells and a vast majority of reactive cells. RS cells produce chemokines that can attract subsets of peripheral blood cells into HL tissues. To gain insight in the chemokines involved in HL, 16 chemokines were selected based on their ability to recruit different subsets of cells. Five HL, 5 non-HL-derived cell lines, 22 HL, 5 non-HL and 3 control tissues were analyzed by reverse transcriptase-polymerase chain reaction (RT-PCR). Products for 13 of these 16 chemokines were detected in 1 or more of the cell lines tested. No or only very faint signals were obtained in HL for CXCL12, CCL7 and CCL8, but CXCL10, CCL5, CCL13, CCL17 and CCL22 were highly or differentially expressed in HL cell lines and tissues. Immunohistochemistry was performed with antibodies reactive with the latter 5 chemokines on paraffin sections of 21 cases of HL. CCL17 and CCL22 had the highest signals in RS cells at gene expression and at protein levels. CCL17 was specific for the classic HL subtypes, whereas CCL22 also had low signals in NLP samples, as well as in some non-HL. CXCL10 was expressed in a large proportion of HL cases with a predominant expression in EBV-positive cases. The results indicate that RS cells produce a complex pattern of chemokines that are involved in the recruitment of reactive cells and contribute to the paradox of an extensive but ineffective host immune response.

Immunohistochemical markers of melanocytic lesions: a review of their diagnostic usefulness

We critically reviewed recent literature reports of 25 melanocytic immunohistochemical markers. This review organizes and summarizes the many new studies of old and novel melanocytic markers and identifies the most promising diagnostic immunohistochemical markers that can be used to distinguish melanocytic from nonmelanocytic lesions and benign melanocytic from malignant melanocytic lesions.

On the regulatory role of dipeptidyl peptidase IV (=CD=adenosine deaminase complexing protein) on adenosine deaminase activity

The molecular mechanism controlling the variable activity of the malignancy marker adenosine deaminase (ADA) is enigmatic. ADA activity was found to be modulated by the membrane-bound adenosine deaminase complexing protein (CP=DPPIV=CD26). The role of lipid-protein interactions in this modulation was sought. While direct solubilization of ADA in vesicles resulted in loss of ADA activity, the binding of ADA to CP reconstituted in vesicles restored the specific activity. The activity of ADA, free or bound to CP in solution, resulted in continuous linear Arrhenius plots. However, ADA bound to reconstituted CP exhibited two breaks associated with approximately 30% increased activity, at 25 and 13 degrees C, yielding three lines with similar apparent activation energies (E(a)). Continuum solvent model calculations of the free energy of transfer of the transmembrane helix of CP from the aqueous phase into membranes of various widths show that the most favorable orientations of the helix above and below the main phase transition may be different. We suggest that the 20% change in the thickness of the bilayer below and above the main phase transition may modify the orientation of CP in the membrane, thereby affecting substrate accessibility of ADA. This could account for ADA's reduced activity associated with increased membrane fluidity in transformed vs. normal fibroblasts.

Chronic inhibition of circulating dipeptidyl peptidase IV by FE 999011 delays the occurrence of diabetes in male zucker diabetic fatty rats

Acute suppression of dipeptidyl peptidase IV (DPP-IV) activity improves glucose tolerance in the Zucker fatty rat, a rodent model of impaired glucose tolerance, through stabilization of glucagon-like peptide (GLP)-1. This study describes the effects of a new and potent DPP-IV inhibitor, FE 999011, which is able to suppress plasma DPP-IV activity for 12 h after a single oral administration. In the Zucker fatty rat, FE 999011 dose-dependently attenuated glucose excursion during an oral glucose tolerance test and increased GLP-1 (7-36) release in response to intraduodenal glucose. Chronic treatment with FE 999011 (10 mg/kg, twice a day for 7 days) improved glucose tolerance, as suggested by a decrease in the insulin-to-glucose ratio. In the Zucker diabetic fatty (ZDF) rat, a rodent model of type 2 diabetes, chronic treatment with FE 999011 (10 mg/kg per os, once or twice a day) postponed the development of diabetes, with the twice-a-day treatment delaying the onset of hyperglycemia by 21 days. In addition, treatment with FE 999011 stabilized food and water intake to prediabetic levels and reduced hypertriglyceridemia while preventing the rise in circulating free fatty acids. At the end of treatment, basal plasma GLP-1 levels were increased, and pancreatic gene expression for GLP-1 receptor was significantly upregulated. This study demonstrates that DPP-IV inhibitors such as FE 999011 could be of clinical value to delay the progression from impaired glucose tolerance to type 2 diabetes.

Interleukin-dependent modulation of HLA-DR expression on CD4and CD8 activated T cells

Summary Interleukins (IL) regulate different T-cell surface Ag known as activation markers that have distinct functional roles. In this paper, while studying the influence of some cytokines(IL-12, IL-2 and IL-4) on the expression of several markers [CD69,CD25, CD26, CD3, human leukocyte antigen (HLA-DR), CD45R0] in in vitro activated human T lymphocytes, we observed two groups of donors responding to phytohaemagglutinin (PHA) activation with high or low HLA-DRAg expression. We also found that CD4 and CD8 populations had different HLA-DR densities under PHA activation (particularly the high HLA-DR-expressing group). Interleukins, in a dose-dependent manner (IL-2 partially),upregulated these HLA-DR levels. In 5 day cultures, IL-12 and IL-2 enhanced the CD8/CD4 ratio of activated T cells,which was responsible, in part, for the IL-dependent HLA-DR upregulation.IL-12 and IL-2 also upregulated the HLA-DR expression at the molecular level on CD8, and IL-12 downregulated it on CD4 cells. It seems that IL-4 upregulated HLA-DR by shortening the mitogen-dependent regulation kinetics. We hypothesize that the different effect of each IL on HLA-DR expression might be related to the regulation of the dose of antigenic peptide presentation and, thus, also influence TH1/TH2 dominance.

Regulation of epithelial and lymphocyte cell adhesion by adenosine deaminase-CD26 interaction

The extra-enzymic function of cell-surface adenosine deaminase (ADA), an enzyme mainly localized in the cytosol but also found on the cell surface of monocytes, B cells and T cells, has lately been the subject of numerous studies. Cell-surface ADA is able to transduce co-stimulatory signals in T cells via its interaction with CD26, an integral membrane protein that acts as ADA-binding protein. The aim of the present study was to explore whether ADA-CD26 interaction plays a role in the adhesion of lymphocyte cells to human epithelial cells. To meet this aim, different lymphocyte cell lines (Jurkat and CEM T) expressing endogenous, or overexpressing human, CD26 protein were tested in adhesion assays to monolayers of colon adenocarcinoma human epithelial cells, Caco-2, which express high levels of cell-surface ADA. Interestingly, the adhesion of Jurkat and CEM T cells to a monolayer of Caco-2 cells was greatly dependent on CD26. An increase by 50% in the cell-to-cell adhesion was found in cells containing higher levels of CD26. Incubation with an anti-CD26 antibody raised against the ADA-binding site or with exogenous ADA resulted in a significant reduction (50-70%) of T-cell adhesion to monolayers of epithelial cells. The role of ADA-CD26 interaction in the lymphocyte-epithelial cell adhesion appears to be mediated by CD26 molecules that are not interacting with endogenous ADA (ADA-free CD26), since SKW6.4 (B cells) that express more cell-surface ADA showed lower adhesion than T cells. Adhesion stimulated by CD26 and ADA is mediated by T cell lymphocyte function-associated antigen. A role for ADA-CD26 interaction in cell-to-cell adhesion was confirmed further in integrin activation assays. FACS analysis revealed a higher expression of activated integrins on T cell lines in the presence of increasing amounts of exogenous ADA. Taken together, these results suggest that the ADA-CD26 interaction on the cell surface has a role in lymphocyte-epithelial cell adhesion.

Regulation of epithelial and lymphocyte cell adhesion by adenosine deaminase-CD26 interaction

The extra-enzymic function of cell-surface adenosine deaminase (ADA), an enzyme mainly localized in the cytosol but also found on the cell surface of monocytes, B cells and T cells, has lately been the subject of numerous studies. Cell-surface ADA is able to transduce co-stimulatory signals in T cells via its interaction with CD26, an integral membrane protein that acts as ADA-binding protein. The aim of the present study was to explore whether ADA-CD26 interaction plays a role in the adhesion of lymphocyte cells to human epithelial cells. To meet this aim, different lymphocyte cell lines (Jurkat and CEM T) expressing endogenous, or overexpressing human, CD26 protein were tested in adhesion assays to monolayers of colon adenocarcinoma human epithelial cells, Caco-2, which express high levels of cell-surface ADA. Interestingly, the adhesion of Jurkat and CEM T cells to a monolayer of Caco-2 cells was greatly dependent on CD26. An increase by 50% in the cell-to-cell adhesion was found in cells containing higher levels of CD26. Incubation with an anti-CD26 antibody raised against the ADA-binding site or with exogenous ADA resulted in a significant reduction (50-70%) of T-cell adhesion to monolayers of epithelial cells. The role of ADA-CD26 interaction in the lymphocyte-epithelial cell adhesion appears to be mediated by CD26 molecules that are not interacting with endogenous ADA (ADA-free CD26), since SKW6.4 (B cells) that express more cell-surface ADA showed lower adhesion than T cells. Adhesion stimulated by CD26 and ADA is mediated by T cell lymphocyte function-associated antigen. A role for ADA-CD26 interaction in cell-to-cell adhesion was confirmed further in integrin activation assays. FACS analysis revealed a higher expression of activated integrins on T cell lines in the presence of increasing amounts of exogenous ADA. Taken together, these results suggest that the ADA-CD26 interaction on the cell surface has a role in lymphocyte-epithelial cell adhesion.

CD26 and CD30 expression on the surface of lymphocyte during normal pregnancy

It is increasingly apparent that the Th1/Th2 cell ratio is decreased during pregnancy. In a previous study, we revealed that combined analysis of soluble CD26 and CD30 might be a potent surrogate tool for evaluating the Th1/Th2 balance during pregnancy. Therefore, in the present study, we elucidated whether the CD26 and CD30 expression on the surface of lymphocyte is useful marker for Th1 and Th2 lymphocytes, respectively, during pregnancy with flow cytometric technique. The peripheral blood samples were obtained from 6 non-pregnant healthy women, 8 healthy pregnant women in the first trimester and 12 pregnant women in the third trimester. The mean percentages of CD26 expression did not differ significantly among these groups (p = 0.45). Also, the mean percentages of CD30 expression did not differ significantly among these groups (p = 0.32). From the present study, the expression of CD26 and CD30 did not appear to be a useful marker for Th1 and Th2 lymphocytes during pregnancy.

Soluble CD26/dipeptidyl peptidase IV enhances transendothelial migration via its interaction with mannose 6-phosphate/insulin-like growth factor II receptor

CD26 is a T cell surface molecule with dipeptidyl peptidase IV (DPPIV) enzyme activity in its extracellular region. In addition to its membrane form, CD26 exists in plasma as a soluble form (sCD26), which is the extracellular domain of the molecule thought to be cleaved from the cell surface. In this paper, we demonstrate that sCD26 mediates enhanced transendothelial T cell migration, an effect that requires its intrinsic DPPIV enzyme activity. We also show that sCD26 directly targets endothelial cells and that mannose 6-phosphate/insulin-like growth factor II receptor (M6P/IGFIIR) on the endothelial cell surface acts as a receptor for sCD26. Our findings therefore suggest that sCD26 influences T cell migration through its interaction with M6P/IGFIIR.

T-cell immune parameters and depression in patients with Crohn's disease

GOALS

The causes of Crohn's disease (CD) are still considered to be unknown. It is likely that an immune defect leads to an increase in T helper 1 (Th1) cytokine responses, which may then contribute to the characteristic morphologic changes. Increased values in distinct immune activation parameters connected with a Th1 immune response have also been found in patients who are depressed. Because various clinical observations have asserted that a depressive disposition may have some connection with the development of CD, we examined whether a relationship exists between T-cell activation parameters and depressive personality characteristics in patients with CD.

STUDY

Seventy-one patients (62% women; age, 38 +/- 13 years) with CD (23 with CD Activity Index [CDAI] >150 and 48 with CDAI < or =150) were included in this study. Sixty patients were re-examined after 4.4 +/- 1.8 months. The T cell parameters CD2, CD3, CD26, CD28, and CD95 and the activity of dipeptidyl peptidase IV (DPP IV) in serum were examined in the peripheral blood. The patient's subjective health status was assessed by means of a standardized psychometric instrument (Short-form Inflammatory Bowel Disease Questionnaire [SIBDQ]). The presence of various characteristics indicative of a depressed mood was also assessed (Center of Epidemiological Studies-Depression Scale, Berliner Stimmungsfragebogen), as well as indicators of a personality disposed to depression (Giessentest) and a depressive illness coping strategy (Freiburger Krankheitsverarbeitungs-Fragebogen), all using the above-mentioned standardized instruments.

RESULTS

The immune parameters connected with the activation of Th1 (CD25+, CD25+/CD26+) are increased in patients, depending on the stage of illness. In addition, DPP IV activity was significantly lower in patients with an active disease, as was their subjective health status (SIBDQ). A connection with an indicator of mental depression could not be found.

CONCLUSION

The observed changes in immune parameters support the idea that morphologic changes could be connected with an increased Th1 response and that DPP IV activity could play an immunomodulatory role. A relationship between the measured immune parameters and individual characteristics of depression could not be found.

Dipeptidyl peptidase IV-like molecules: homologous proteins or homologous activities?

Membrane-bound proteases are widely distributed among various cell systems. Their expression in a particular cell type is finely regulated, reflecting the specific functional cell implications and engagement in defined physiological pathways. Protein turnover, ontogeny, inflammation, tissue remodeling, cell migration and tumor invasion are among the many physiological and pathological events in which membrane proteases play a crucial role, both as effector as well as regulatory molecules. The presence of proline residues gives unique structural features to peptide chains, substantially influencing the susceptibility of proximal peptide bond to protease cleavage. Among the rare group of proline-specific proteases, dipeptidyl peptidase IV (DPP-IV, EC 3.4.14.5) was originally believed to be the only membrane-bound enzyme specific for proline as the penultimate residue at the amino-terminus of the polypeptide chain. However, other molecules, even structurally non-homologous with the DPP-IV but bearing corresponding enzyme activity, have been identified recently. This review summarizes the present knowledge of "DPP-IV activity- and/or structure-homologues" (DASH) and provides some insight into their multifunctional roles.

Dipeptidyl peptidase IV (DP IV, CD26) in patients with inflammatory bowel disease

BACKGROUND

Dipeptidyl peptidase IV (DP IV, CD26), a serine protease with broad tissue distribution and known activity in serum, participates in T cell activation and promotes a Th1 cytokine response, a function in part attributable to its enzymatic activity. We hypothesized that the activity of DP IV in serum and expression of CD26/DP IV in lymphocytes may be altered in patients with inflammatory bowel disease (IBD).

METHODS

Serum DP IV activity and CD26 (DP IV)-positive peripheral blood lymphocytes were measured in 110 patients with IBD (Crohn disease (CD): n = 63, ulcerative colitis (UC): n = 47). Additionally, T cell activation antigens (CD25, CD95) and costimulatory molecules (CD28) were evaluated. The same analyses were carried out in healthy volunteers (HC, n = 28). Thirty-nine patients with CD and 28 patients with UC were reassessed 3-6 months after the first visit.

RESULTS

In patients with IBD, the DP IV activity in serum was reduced (mean +/- s (standard deviation): 52.8 U/l +/- 16.9 (CD) and 55.7 +/- 15.1 U/l (UC) versus 71.9 +/- 18.4 (HC), P < 0.001). Furthermore, patients with IBD had higher numbers of CD26-positive cells coexpressing CD25 and a higher surface expression of CD26 (DP IV) (mean fluorescence intensity, mean 57.1 (CD) and 59.8 (UC) versus 29.9 (HC), P < 0.001). The DP IV activity in serum showed an inverse correlation with known disease activity scores as well as with the concentrations of orosomucoid in serum.

CONCLUSION

The changes of DP IV in patients with IBD highlight alterations at an interface between immune function and metabolism of peptide hormones, with potential importance for the pathophysiology of IBD. Furthermore, these changes may help to refine the assessment of IBD activity.

Antigen presentation of Type II collagen in rats

Collagen-induced arthritis (CIA) is a T-cell dependent disease of rats which follows immunization with bovine type II collagen (bCII). Susceptibility to CIA is linked to the genes encoding the major histocompatibility complex (MHC), suggesting that antigen presentation is important in disease pathogenesis. Antigen-presenting cells (APC) (macrophages, dendritic cells (DC) and B cells) were prepared from WA/KIR/KCL rats and presentation of antigen, in the form of native protein (bCII) or synthetic peptide (bCII:184-198), was assessed in T-cell proliferation assays. Whilst macrophages inhibited proliferative responses to bCII, splenic or thymic low density cells, enriched for DC, presented both bCII and bCII(184-198) peptide. However, bone marrow-derived DC, which stimulated T-cell responses to OVA, failed to present bCII, suggesting differences in processing of these two antigens. B-cell depletion from lymph node cells abrogated the proliferative response to bCII and reconstitution of a T-cell population with B cells restored the proliferative response, indicating that B cells are important for stimulating T-cell responses to bCII. B cells play a critical role in CIA by producing pathogenic anti-bCII antibodies, and we propose that B cells are also important APC which present bCII to CD4+ T cells.

Cell surface human alpha-L-fucosidase

The acid alpha-L-fucosidase is usually found as a soluble component of lysosomes where fucoglycoconjugates are degraded. In the present investigation, we have demonstrated the existence of a cell surface protein with enzymatic alpha-L-fucosidase activity that crossreacts specifically with a rabbit anti-(alpha-L-fucosidase) Ig. By different approaches, this alpha-L-fucosidase, which represents 10-20% of the total cellular fucosidase activity, was detected in all the tested human cells (hemopoietic, epithelial, mesenchymal). Two bands of approximately 43-49 kDa were observed, although theoretical data support the possibility of having the same genetic origin that the known 50 to 55-kDa Mr alpha-L-fucosidase. We speculate about an alternative traffic pathway for the plasma membrane alpha-L-fucosidase to work on the rapid turnover of glycoproteins.

Interaction of plasminogen with dipeptidyl peptidase IV initiates a signal transduction mechanism which regulates expression of matrix metalloproteinase-9 by prostate cancer cells

Both plasminogen (Pg) activation and matrix metalloproteinases (MMPs) are involved in the proteolytic degradation of extracellular matrix components, a requisite event for malignant cell metastasis. The highly invasive 1-LN human prostate tumour cell line synthesizes and secretes large amounts of Pg activators and MMPs. We demonstrate here that the Pg type 2 (Pg 2) receptor in these cells is composed primarily of the membrane glycoprotein dipeptidyl peptidase IV (DPP IV). Pg 2 has six glycoforms that differ in their sialic acid content. Only the highly sialylated Pg 2gamma, Pg 2delta and Pg 2epsilon glycoforms bind to DPP IV via their carbohydrate chains and induce a Ca(2+) signalling cascade; however, Pg 2epsilon alone is also able to significantly stimulate expression of MMP-9. We further demonstrate that the Pg-mediated invasive activity of 1-LN cells is dependent on the availability of Pg 2epsilon. This is the first demonstration of a direct association between the expression of MMP-9 and the Pg activation system.

Rapid inactivation of stromal cell-derived factor-1 by cathepsin G associated with lymphocytes

The CXC chemokine stromal cell-derived factor (SDF)-1 is produced constitutively in different tissues. It is the only known ligand for CXCR4, which is widely expressed in leukocytes and in some tissue cells, and acts as coreceptor for X4 HIV strains. Because of the general interest in the mechanisms that regulate the activity of constitutively expressed chemokines, we have studied the inactivation of SDF-1 in cells that bear CXCR4. Here we show that B lymphocytes, NK cells and, to a lesser extent, T lymphocytes inactivate SDF-1 by N-terminal processing. Inactivation is due to cathepsin G which is associated with the membrane of lymphocytes and rapidly cleaves off five N-terminal residues by acting on the Leu(5)-Ser(6) bond yielding SDF-1(6-67). Processing was observed with intact cells, cell membrane preparations and soluble cathepsin G obtained by extraction of the membranes with Triton X-100. Cathepsin G is released by neutrophils and monocytes and binds on the surface of lymphocytes by an apparently saturable process. Analysis of the product obtained, the time course and the sensitivity to inhibitors shows that cathepsin G is the only protease involved. Conversion of SDF-1 to SDF-1(6-67) was complete within minutes to 1-2 h depending on the enzyme source, and was abrogated by inhibitors of serine proteases and chymostatin. Diprotin A, an inhibitor of dipeptidyl peptidase IV, was without effect. Owing to its availability on the surface of SDF-1-responsive cells and its rapid effect, cathepsin G is likely to play a significant role in down-regulating SDF-1 activity.