Impact of diabetes on neutrophil-to-lymphocyte ratio and its relationship to coronary artery disease

BACKGROUND

Coronary artery disease (CAD) is the leading cause of mortality among diabetic patients, and the neutrophil-to-lymphocyte ratio (NLR) has recently emerged from among inflammatory parameters as a potential indicator of vascular complications and poorer outcome in patients with diabetes. This study aimed to evaluate: 1) the impact of diabetes on NLR; and 2) the role of NLR on the extent of CAD among diabetic patients undergoing coronary angiography.

METHODS

Consecutive patients undergoing coronary angiography were included. Diabetic status and main chemistry parameters were assessed at the time of admission. Significant CAD was defined as at least one vessel with stenosis>50%, while severe CAD was left main and/or three-vessel disease, as evaluated by quantitative coronary angiography (QCA).

RESULTS

Diabetes was observed in 1377 of 3756 patients (36.7%); they were older, and displayed higher-risk cardiovascular profile and more complex CAD. Diabetic status was also associated with a significant increase in NLR (P=0.004). Among diabetics, higher NLR tertile values were related to ageing (P<0.001), dyslipidaemia (P<0.001), renal failure (P<0.001), body mass index (P<0.001), previous percutaneous coronary revascularization (P=0.004) and cerebrovascular events (P=0.003), acute presentation (P<0.001), treatment at admission with beta-blockers/statins/ASA (all P<0.001), diuretics (P=0.01) or clopidogrel (P=0.04), platelet count (P=0.03), white blood cell count, creatinine, glycaemia and C-reactive protein (P<0.001), and inversely related to haemoglobin, triglyceride levels (P<0.001) and smoking (P=0.03). NLR was associated with multivessel disease (P<0.001), degree of stenosis (P=0.01), type C lesions (P=0.02), coronary calcifications and intracoronary thrombus (P<0.001), but inversely with in-stent restenosis (P=0.003) and TIMI flow grade (P=0.02). Also, NLR was directly related to CAD prevalence (P<0.001; adjusted OR [95% CI]: 1.62 [1.27-2.07], P<0.001) and CAD severity (P<0.001; adjusted OR [95% CI]: 1.19 [1.00-1.43], P=0.05).

CONCLUSION

NLR is increased among diabetic patients and, in such patients, is independently associated with the prevalence and severity of CAD. Further studies are now needed to confirm present results and to evaluate the underlying pathophysiological mechanisms behind our findings.

Human platelets express authentic CB₁ and CB₂ receptors

In the last decade, the neurovascular effects exerted by endocannabinoids (eCBs) have attracted growing interest, because they hold the promise to open new avenues of therapeutic intervention against major causes of death in Western society. Several actions of eCBs are mediated by type-1 (CB₁) or type-2 (CB₂) cannabinoid receptors, yet there is no clear evidence of the presence of these proteins in platelets. To demonstrate that CB₁ and CB₂ are expressed in human platelets, we analyzed their protein level by Western blotting and ELISA, visualized their cellular localization by confocal microscopy, and ascertained their functionality by binding assays. We found that CB₁, and to a lesser extent CB₂, are expressed in highly purified human platelets. Both receptor subtypes were predominantly localized inside the cell, thus explaining why they might remain undetected in preparations of plasma membranes. The identification of authentic CB₁ and CB₂ in human platelets supports the potential exploitation of selective agonists or antagonists of these receptors as novel therapeutics to combat neurovascular disorders. It seems remarkable that some of these substances have been already used in humans to treat disease states.

The endocannabinoid 2-arachidonoylglycerol activates human platelets through non-CB1/CB2 receptors

BACKGROUND

The endocannabinoid 2-arachidonoylglycerol (2-AG) is an endogenous lipid that acts through the activation of G-protein-coupled cannabinoid receptors and plays essential roles in many physiological contexts. In the cardiovascular system 2-AG is generated by both activated endothelial cells and platelets, and participates in the regulation of inflammation and thrombosis. Although human platelets actively metabolize endocannabinoids, 2-AG also binds to platelet surface and leads to cell activation.

OBJECTIVE

To investigate the biological consequence of 2-AG interactions with human platelets and to clarify the role of cannabinoid receptors.

METHODS

Gel-filtered platelets were stimulated with 2-AG in the presence or absence of various inhibitors. Platelet aggregation and secretion were measured in a lumiaggregometer. Calcium ion movements were measured in FURA-2 loaded platelets. Thromboxane A(2) (TxA(2)) generation was evaluated as Thromboxane B(2) accumulation with a commercial EIA assay.

RESULTS

2-AG induced platelet shape change, aggregation and secretion with a dose-dependent mechanism that required engagement of platelet TxA(2) receptors. 2-AG caused also cytosolic calcium increase; however, it was totally dependent on availability of TxA(2). Indeed 2-AG was able to induce a robust generation of TxA(2) through the cyclooxygenase pathway. Treatment of platelets with inhibitors of monoacylglycerol lipase and fatty acid amide hydrolase did not affect the activation induced by 2-AG. Moreover, neither CB(1) and CB(2) proteins nor CB(1)/CB(2) mRNAs were detected in platelets.

CONCLUSIONS

2-AG can be considered a new physiologic platelet agonist able to induce full platelet activation and aggregation with a non-CB(1)/CB(2) receptor-mediated mechanism.

Diacylglycerol kinase-alpha phosphorylation by Src on Y335 is required for activation, membrane recruitment and Hgf-induced cell motility

Diacylglycerol (DAG) kinases (Dgk), which phosphorylate DAG to generate phosphatidic acid, act as either positive or negative key regulators of cell signaling. We previously showed that Src mediates growth factors-induced activation of Dgk-alpha, whose activity is required for cell motility, proliferation and angiogenesis. Here, we demonstrate that both hepatocytes growth factor (HGF) stimulation and v-Src transformation induce tyrosine phosphorylation of Dgk-alpha on Y335, through a mechanism requiring its proline-rich C-terminal sequence. Moreover, we show that both proline-rich sequence and phosphorylation of Y335 of Dgk-alpha mediate: (i) its enzymatic activation, (ii) its ability to interact respectively with SH3 and SH2 domains of Src, (iii) its recruitment to the membrane. In addition, we show that phosphorylation of Dgk-alpha on Y335 is required for HGF-induced motility, while its constitutive recruitment at the membrane by myristylation is sufficient to trigger spontaneous motility in absence of HGF. Providing the first evidence that tyrosine phosphorylation of Dgk-alpha is required for growth-factors-induced activation and membrane recruitment, these findings underscore its relevance as a rheostat, whose activation is a threshold to elicit growth factors-induced migratory signaling.

Activation of the small GTPase Rap2B in agonist-stimulated human platelets

The activation of the small GTPase Rap2B in resting and agonist-stimulated human platelets was investigated. Both thrombin, that stimulates heterotrimeric G-protein-coupled receptors, and the GPVI ligand convulxin, that activates a tyrosine-kinase based signaling pathway, were able to induced the rapid and sustained binding of GTP to Rap2B. Similarly, a number of other agonists tested, previously known to activate the highly related protein Rap1B, were also able to stimulate Rap2B. In contrast, platelet antagonists that increase the intracellular concentration of cAMP did not signal to Rap2B. Thrombin- and convulxin-induced activation of Rap2B was not dependent on thromboxane A2, did not require the interaction of the protein with the cytoskeleton, and was not regulated by integrin alphaIIbbeta3-dependent outside-in signaling. When secreted ADP was neutralized, activation of Rap2B induced by thrombin, but not by convulxin, was significantly reduced. ADP itself was found to induce the rapid and sustained binding of GTP to Rap2B, and this effect was predominantly mediated by stimulation of the Gi-coupled P2Y12 receptor. Activation of Rap2B promoted by both thrombin and convulxin was regulated by intracellular Ca2+, while protein kinase C was found to be involved in convulxin- but not in thrombin-induced activation of Rap2B. Moreover, Rap2B activation induced by thrombin, but not by convulxin, was totally dependent on phosphatidylinositol 3-kinase activity. These results demonstrate that the small GTPase Rap2B is involved in platelet activation, and outline some important differences between the regulation of highly related GTPases Rap2B and Rap1B in human platelets.

Triggering receptor expressed on myeloid cells: role in the diagnosis of lung infections

The triggering receptor expressed on myeloid cells (TREM)-1 is a recently described molecule, which plays an important role in myeloid cell-activated inflammatory responses. TREM-1 is expressed on blood neutrophils and monocytes, and also on alveolar macrophages, thus suggesting a potential role in lung inflammatory responses against infections. To investigate the differential expression of TREM-1 in lung infections, its levels were assessed in bronchoalveolar lavage specimens from patients with community-acquired pneumonia or tuberculosis. TREM-1 was also investigated in patients with interstitial lung diseases, as a model of noninfectious inflammatory disease of the lung. TREM-1 expression was significantly increased in lung neutrophils and in lung macrophages of patients with pneumonia (n=7; 387.9+/-61.4 and 660.5+/-18.3, respectively) compared with patients with pulmonary tuberculosis (n=7; 59.2+/-13.1 and 80.6+/-291.2) and patients with interstitial lung diseases (n=10; 91.8+/-23.3 and 123.9+/-22.8). In contrast, TREM-1 expression on peripheral blood neutrophils was no different among the three groups. In conclusion, these data suggest that triggering receptor expressed on myeloid cells-1 is selectively expressed in the lungs of patients with pneumonia caused by extracellular bacteria and not in patients with tuberculosis, providing a potential marker for differential diagnosis.

Gene expression profiling in immune cells using microarray

The recent development of DNA microarray, which offers the opportunity to study the expression of thousands of individual genes simultaneously in different biological systems, has provided new insights into the immune system. Examples discussed in this review include molecular descriptions of the differentiation program of T helper (Th) cells into Th1 and Th2 pathways and the genetic program underlying maturation of dendritic cells. It is anticipated that this new information can be used to understand gene function in both physiological and pathological conditions of the immune system.

Unique chemotactic response profile and specific expression of chemokine receptors CCR4 and CCR8 by CD4(+)CD25(+) regulatory T cells

Chemokines dictate regional trafficking of functionally distinct T cell subsets. In rodents and humans, a unique subset of CD4(+)CD25(+) cytotoxic T lymphocyte antigen (CTLA)-4(+) regulatory T cells (Treg) has been proposed to control peripheral tolerance. However, the molecular basis of immune suppression and the trafficking properties of Treg cells are still unknown. Here, we determined the chemotactic response profile and chemokine receptor expression of human blood-borne CD4(+)CD25(+) Treg cells. These Treg cells were found to vigorously respond to several inflammatory and lymphoid chemokines. Treg cells specifically express the chemokine receptors CCR4 and CCR8 and represent a major subset of circulating CD4(+) T cells responding to the chemokines macrophage-derived chemokine (MDC)/CCL22, thymus and activation-regulated chemokine (TARC)/CCL17, I-309/CCL1, and to the virokine vMIP-I (ligands of CCR4 and CCR8). Blood-borne CD4(+) T cells that migrate in response to CCL1 and CCL22 exhibit a reduced alloproliferative response, dependent on the increased frequency of Treg cells in the migrated population. Importantly, mature dendritic cells preferentially attract Treg cells among circulating CD4(+) T cells, by secretion of CCR4 ligands CCL17 and CCL22. Overall, these results suggest that CCR4 and/or CCR8 may guide Treg cells to sites of antigen presentation in secondary lymphoid tissues and inflamed areas to attenuate T cell activation.

Platelet activation by von Willebrand factor requires coordinated signaling through thromboxane A2 and Fc gamma IIA receptor

Interaction of von Willebrand Factor with glycoprotein Ib-IX-V induces platelet activation through a still poorly defined mechanism. Previous studies have suggested a possible role for the low affinity receptor for immunoglobulin, Fc gamma RIIA, in GPIb-IX-V signaling. Here we show that binding of vWF to platelets induces the tyrosine phosphorylation of Fc gamma RIIA by a Src kinase. Treatment of platelets with the anti-Fc gamma RIIA monoclonal antibody IV.3 specifically inhibits vWF-induced but not thrombin-induced pleckstrin phosphorylation and serotonin secretion. Moreover, vWF fails to induce pleckstrin phosphorylation in mouse platelets, lacking Fc gamma RIIA, and serotonin secretion is impaired. Pleckstrin phosphorylation and serotonin secretion in human platelets stimulated with vWF are blocked by the cyclooxygenase inhibitor acetylsalicylic acid. However, release of arachidonic acid and synthesis of TxA(2) induced by vWF are not affected by the anti-Fc gamma RIIA monoclonal antibody IV.3. Similarly, vWF-induced tyrosine phosphorylation of Fc gamma RIIA, as well as of Syk and PLC gamma 2, occurs normally in aspirinized platelets. Inhibition of the tyrosine kinase Syk by piceatannol does not affect vWF-induced tyrosine phosphorylation of Fc gamma RIIA but prevents phosphorylation of PLC gamma 2. Pleckstrin phosphorylation and platelet secretion induced by vWF, but not by thrombin, are also inhibited by piceatannol. Pleckstrin phosphorylation is also sensitive to the phosphatidylinositol 3-kinase inhibitor wortmannin. These results indicate that PLC gamma 2 plays a central role in platelet activation by vWF and that the stimulation of this enzyme requires coordinated signals through endogenous TxA(2) and Fc gamma RIIA.

The C-C chemokine receptors CCR4 and CCR8 identify airway T cells of allergen-challenged atopic asthmatics

In vitro polarized human Th2 cells preferentially express the chemokine receptors CCR3, CCR4, and CCR8 and migrate to their ligands: eotaxin, monocyte-derived chemokine (MDC), thymus- and activation-regulated chemokine (TARC), and I-309. We have studied the expression of chemokines and chemokine receptors in the airway mucosa of atopic asthmatics. Immunofluorescent analysis of endobronchial biopsies from six asthmatics, taken 24 hours after allergen challenge, demonstrates that virtually all T cells express IL-4 and CCR4. CCR8 is coexpressed with CCR4 on 28% of the T cells, while CCR3 is expressed on eosinophils but not on T cells. Expression of the CCR4-specific ligands MDC and TARC is strongly upregulated on airway epithelial cells upon allergen challenge, suggesting an involvement of this receptor/ligand axis in the regulation of lymphocyte recruitment into the asthmatic bronchi. In contrast to asthma, T cells infiltrating the airways of patients with chronic obstructive pulmonary disease and pulmonary sarcoidosis produce IFN-gamma and express high levels of CXCR3, while lacking CCR4 and CCR8 expression. These data support the role of CCR4, of its ligands MDC and TARC, and of CCR8 in the pathogenesis of allergen-induced late asthmatic responses and suggest that these molecules could be considered as targets for therapeutic intervention.

Fractalkine (CX3CL1) as an amplification circuit of polarized Th1 responses

Fractalkine (FKN, CX3CL1) is a membrane-bound CX3C chemokine induced by primary proinflammatory signals in vascular endothelial cells (ECs). Here we examined the role of FKN in polarized Th1 or Th2 responses. Proinflammatory signals, including LPS, IL-1, TNF, and CD40 ligand, induced FKN, as did IFN-gamma, which had synergistic activity with TNF. IL-4 and IL-13 did not stimulate the expression of FKN and markedly reduced induction by TNF and IFN-gamma. TNF alone or combined with IFN-gamma also induced release of soluble FKN, which was inhibited by IL-4 and IL-13. In light of this differential regulation of FKN by the master cytokines that control polarized responses, we analyzed the interaction of FKN with natural killer (NK) cells and polarized T-cell populations. NK cells expressed high levels of the FKN receptor CX3CR1 and responded to FKN. CX3CR1 was preferentially expressed in Th1 compared with Th2 cells. Th1 but not Th2 cells responded to FKN. By immunohistochemistry, FKN was expressed on ECs in psoriasis, a Th1-dominated skin disorder, but not in Th2-driven atopic dermatitis. Similarly, ECs in Mycobacterium tuberculosis granulomatous lymphadenitis, but not those in reactive lymph node hyperplasia or in Castelman's disease, showed immunoreactive FKN. These results indicate that regulated expression of FKN in ECs participates in an amplification circuit of polarized type I responses.

Regulation of helper T cell differentiation and recruitment in airway inflammation

CD4(+) helper T type 1 (Th1) and Th2 cells are critical mediators of inflammatory diseases. Although T cells represent only a fraction of the leukocytes that are found in the lung during inflammation, they play a critical role in coordinating the immune response to infectious agents and allergens. T cells have the ability to rapidly expand in response to specific stimuli and to differentiate into effector cells that, through the production of soluble factors such as cytokines and chemokines, communicate with other cells to initiate a cascade of inflammatory events. The objective of this review is to outline the cellular and molecular mechanisms involved in the generation and recruitment of Th1 and Th2 cells in the lung. Defining these mechanisms should lead to improved immunopharmacological strategies for prophylaxis and therapy.

Selective inhibition of HIV replication in primary macrophages but not T lymphocytes by macrophage-derived chemokine

Macrophage-derived chemokine (MDC) has been reported to inhibit different HIV-1 strains in activated peripheral blood mononuclear cells (T cell blasts), although other investigators have not confirmed these findings. Here we demonstrate that MDC inhibits the replication of CCR5-dependent (R5) HIV-1(BaL) in monocyte-derived macrophages (MDM), but not in T cell blasts, although with variable potency depending on donor variability. Analysis of HIV-1(BaL) proviral DNA synthesis in MDM indicated that the suppressive effect of MDC did not involve inhibition of early events such as entry or reverse transcription. Finally, an inverse correlation was observed between the levels of endogenous MDC secreted by uninfected MDM of different donors and the efficiency of different HIV strains, including two primary isolates with different coreceptor usage, to replicate in these cells. Thus, MDC represents an example of a chemokine inhibiting HIV replication in macrophages acting at one or more postentry levels in the virus life cycle.

Proliferative responses to selected peptides of IA-2 in identical twins discordant for Type 1 diabetes

BACKGROUND

The aim of the study was to define T lymphocyte reactivity to selected peptides of an islet antigen IA-2, associated with Type 1 diabetes.

METHODS

We used 10 peptides selected from the IA-2 molecule due to their predicted ability to bind to HLA-DRB1*0401, a Type 1 diabetes-associated allele. We tested 21 identical twin pairs discordant for the disease and 15 control subjects and then followed them prospectively; seven non-diabetic twins developed diabetes.

RESULTS

Twins of identical pairs tended to respond to different peptides suggesting that the T cell response is, to a degree, shaped by non-genetically determined factors (p<0. 0001). However, there was no difference in the T cell responses between diabetic twins and either their non-diabetic identical twins or control subjects and the response was heterogenous. T cell responses did not differ in those seven non-diabetic twins who developed diabetes from those twins who did not. T cell responses to peptide 11 (amino acids 502-514) was immunodominant in diabetic twins as well as their non-diabetic twins and controls; responses were not correlated with HLA, IA-2 antibodies, age or duration of disease.

CONCLUSION

We conclude that T cell responses to selected IA-2 peptides are not genetically determined, heterogeneous, not strictly HLA controlled and did not distinguish diabetic or prediabetic twins from non-diabetic twins or controls. The identification of an immunodominant T cell response to IA-2 peptide 502-514 raises the possibility that this, or similar, epitopes may be of therapeutic value in disease prevention.

Transcript imaging of the development of human T helper cells using oligonucleotide arrays

Many pathological processes, including those causing allergies and autoimmune diseases, are associated with the presence of specialized subsets of T helper cells at the site of inflammation. Understanding the genetic program that controls the functional properties of T helper type 1 (Th1) versus T helper type 2 (Th2) cells may provide insight into the pathophysiology of inflammatory diseases. We compared the gene-expression profiles of human Th1 and Th2 cells using high-density oligonucleotide arrays with the capacity to display transcript levels of 6,000 human genes. Here we analyse the data sets derived from five independent experiments using statistical algorithms. This approach resulted in the identification of 215 differentially expressed genes, encoding proteins involved in transcriptional regulation, apoptosis, proteolysis, and cell adhesion and migration. A subset of these genes was further upregulated by exposure of differentiated Th1 cells to interleukin-12 (IL-12), as confirmed by kinetic PCR analysis, indicating that IL-12 modulates the effector functions of Th1 cells in the absence of antigenic stimulation. Functional assays and in vivo expression of selected genes have validated the biological relevance of our study. Our results provide new insight into the transcriptional program controlling the functional diversity of subsets of T helper cells.

Inhibition by IL-12 and IFN-alpha of I-309 and macrophage-derived chemokine production upon TCR triggering of human Th1 cells

Th1 and Th2 cells, which produce distinct sets of cytokines, differentially express several chemokine receptors that may regulate their tissue-specific localization. Although the expression pattern and regulation of chemokines are likely to play a critical role in many immunopathological processes, they remain largely unknown. Here, we investigated the requirements for Th1 and Th2 cells to produce the Th2 cell-attracting chemokines thymus and activation-regulated chemokine (TARC), macrophage-derived chemokine (MDC) and I-309. TCR triggering of Th1 and Th2 cells leads to production of MDC and I-309 (CCR4 and CCR8 ligands, respectively), whereas TARC (CCR4 ligand) is selectively produced by Th2 cells. Secretion of these chemokines appears to be independent of endogenous production of IL-4 and IFN-gamma. IL-12 and IFN-alpha, cytokines that promote the differentiation of human Th1 cells, selectively inhibit secretion and mRNA expression of MDC and I-309 by Th1 cells. Suppression of I-309 secretion results in a decreased chemotactic effect on L1.2 cells transfected with human CCR8, indicating that IL-12 and IFN-alpha may inhibit the recruitment of CCR8-expressing cells such as Th2 cells. The inhibition of Th2 cell-attracting chemokines MDC and I-309 illustrates a novel mechanism by which IL-12 and IFN-alpha could promote and maintain an ongoing Th1 response.

Chemokines fail to up-regulate beta 1 integrin-dependent adhesion in human Th2 T lymphocytes

Th1 and Th2 cells are functionally distinct subsets of CD4+ T lymphocytes whose tissue-specific homing to sites of inflammation is regulated in part by the differential expression of P- and E-selectin ligands and selected chemokine receptors. Here we investigated the expression and function of beta 1 integrins in Th1 and Th2 cells polarized in vitro. Th1 lymphocytes adhere transiently to the extracellular matrix ligands laminin 1 and fibronectin in response to chemokines such as RANTES and stromal cell-derived factor-1, and this process is paralleled by the activation of the Rac1 GTPase and by a rapid burst of actin polymerization. Selective inhibitors of phosphoinositide-3 kinase prevent efficiently all of the above processes, whereas the protein kinase C inhibitor bisindolylmaleimide prevents chemokine-induced adhesion without affecting Rac1 activation and actin polymerization. Notably, chemokine-induced adhesion to beta 1 integrin ligands is markedly reduced in Th2 cells. Such a defect cannot be explained by a reduced sensitivity to chemokine stimulation in this T cell subset, nor by a defective activation of the signaling cascade involving phosphoinositide-3 kinase, Rac1, and actin turnover, as all these processes are activated at comparable levels by chemokines in the two subsets. We propose that reduced beta 1 integrin-mediated adhesion in Th2 cells may restrain their ability to invade and/or reside in sites of chronic inflammation, which are characterized by thickening of basement membranes and extensive fibrosis, requiring efficient interaction with organized extracellular matrices.

The platelet cytoskeleton regulates the aggregation-dependent synthesis of phosphatidylinositol 3,4-bisphosphate induced by thrombin

Pretreatment of intact platelets with cytochalasin D prevented actin polymerization and cytoskeleton reorganization induced by thrombin, but did not affect platelet aggregation. Under these conditions, synthesis of phosphatidylinositol 3,4-bisphosphate (PtdIns(3,4)P2) stimulated by thrombin was strongly inhibited, while production of phosphatidic acid was unaffected. The inhibitory effect of cytochalasin D was not observed when platelet aggregation was prevented by the RGDS peptide. We also found that cytochalasin D did not affect PtdIns(3,4)P2 synthesis induced by concanavalin A (ConA), which is known to occur through an aggregation-independent mechanism. Moreover, thrombin, but not ConA, induced the translocation of phosphatidylinositol 3-kinase to the cytoskeleton. This process was equally inhibited by both the RGDS peptide and cytochalasin D. These results demonstrate that the cytoskeleton represents a functional link between thrombin-induced aggregation and synthesis of PtdIns(3,4)P2.

Interaction of the low-molecular-weight GTP-binding protein rap2 with the platelet cytoskeleton is mediated by direct binding to the actin filaments

The interaction of the low-molecular-weight GTP-binding protein rap2 with the cytoskeleton from thrombin-aggregated platelets was investigated by inducing depolymerization of the actin filaments, followed by in vitro-promoted repolymerization. We found that the association of rap2 with the cytoskeleton was spontaneously restored after one cycle of actin depolymerization and repolymerization. Exogenous rap2, but not unrelated proteins, added to depolymerized actin and solubilized actin-binding proteins, was also specifically incorporated into the in vitro reconstituted cytoskeleton. The incorporation of exogenous rap2 was also observed when the cytoskeleton from resting or thrombin-activated platelets was subjected to actin depolymerization-repolymerization. Moreover, such interaction occurred equally well when exogenous rap2 was loaded with either GDP or GTPgammaS. We also found that polyhistidine-tagged rap2 immobilized on Ni(2+)-Sepharose and loaded with either GDP or GTPgammaS, could specifically bind to cytoskeletal actin. Moreover, when purified monomeric actin was induced to polymerize in vitro in the presence of rap2, the small G-protein specifically associated with the actin filaments. Finally, rap2 loaded with either GDP or GTPgammaS was able to bind to purified F-actin immobilized on a plastic surface. These results demonstrate that rap2 interacts with the platelet cytoskeleton by direct binding to the actin filaments and that this interaction is not regulated by the activation state of the protein.

Substitution of aspartic acid at beta57 with alanine alters MHC class II peptide binding activity but not protein stability: HLA-DQ (alpha1*0201, beta1*0302) and (alpha1*0201, beta1*0303)

In class II major histocompatibility complex (MHC) proteins, residue beta57 is usually aspartic acid. Alleles carrying serine, valine, or alanine at this position are strongly correlated with the development of insulin-dependent diabetes mellitus (IDDM). Asp(beta)57 participates in a conserved salt bridge that bridges the alpha and beta subunits in the peptide-binding site. It has been proposed that the correlation between IDDM and MHC alleles lacking Asp(beta)57 may be due to an instability of the protein caused by loss of this salt bridge. Using a pair of HLA-DQ proteins (alpha1*0201, beta1*0302) and (alpha1*0201, beta1*0303) differing only in having aspartic acid or alanine at position beta57, we show that the polymorphism does not have a significant effect on protein stability for either the empty or peptide-loaded forms. However, the circular dichroism spectra indicate that empty and peptide-loaded Alabeta57 proteins display slightly different secondary structures relative to their Aspbeta57 counterparts. A set of three peptides shows different binding affinities for DQ(alpha1*0201, beta1*0302) relative to DQ(alpha1*0201, beta1*0303). We propose that substitution of Asp(beta)57 residue causes a local rearrangement within the DQ peptide-binding site that alters the peptide-binding specificity. This rearrangement may help to explain the previously observed differences in SDS stability between Asp and non-Asp(beta)57 DQ proteins.

Upregulation of integrin alpha6/beta1 and chemokine receptor CCR1 by interleukin-12 promotes the migration of human type 1 helper T cells

CD4(+) T helper 1 (Th1) cells and Th2 cells are distinguished based on the pattern of cytokines they are able to produce. Selectin ligands and chemokine receptors are differentially expressed in Th1 and Th2 cells, providing a basis for tissue-specific recruitment of helper T-cell subsets. However, the modes and mechanisms regulating tissue-specific localization of Th1 and Th2 cells are still largely unknown. Here, we show the preferential expression on Th1 cells of the integrin alpha6/beta1, which is distinctly regulated by the Th1-inducing cytokines interleukin-12 (IL-12) and interferon-alfa (IFN-alpha). The pattern of integrin alpha6/beta1 regulation closely mirrors that of the chemokine receptor CCR1. Analysis of signal transducer and activator of transcription 4 (Stat4) activation by IL-12 and IFN-alpha shows distinct signaling kinetics by these cytokines, correlating with the pattern of CCR1 and integrin alpha6/beta1 expression. Unlike IFN-alpha, the ability of IL-12 to generate prolonged intracellular signals appears to be critical for inducing integrin alpha6/beta1 upregulation in Th1 cells. The expression and upregulation of CCR1 and alpha6/beta1 integrin promotes the migration of Th1 cells. These findings suggest that the exquisite regulation of integrin alpha6/beta1 and CCR1 may play an important role in tissue-specific localization of Th1 cells.

Type I interferons and the Th1/Th2 paradigm

During the past year significant advances have been made in our understanding of the factors contributing to the differentiation of CD4+ T helper cell subsets. These have been driven, in part, by the realization that cytokines from the innate immune response, such as interleukin-12 (IL-12) and interferons (IFNs), play a critical role in T cell subset differentiation. This review covers some of the most recent data concerning the divergent role that IFNs have in the differentiation of human versus mouse T helper cell subsets. In this review we discuss the molecular basis for the specie-specific effect of type I IFN on the selective induction of Th1 type immune responses. Furthermore, since IFN-beta is used in the treatment of multiple sclerosis (MS) we discuss the potential effects of such treatment and the value of the Th1/Th2 paradigm in MS.

Envelope-dependent restriction of human immunodeficiency virus type 1 spreading in CD4(+) T lymphocytes: R5 but not X4 viruses replicate in the absence of T-cell receptor restimulation

The human immunodeficiency virus (HIV) replicates in activated CD4(+) T lymphocytes. However, only CD4(+) Th2 and Th0, but not Th1, CD4(+) T-cell clones have been reported to efficiently support HIV-1 replication. This dichotomous pattern was further investigated in the present study in Th1, Th2, or Th0 cell lines derived from umbilical human cord blood and in T-cell clones obtained from the peripheral blood mononuclear cells (PBMC) of healthy adults. Both primary and laboratory-adapted HIV-1 strains with CCR5 as the exclusive entry coreceptor (R5 viruses) efficiently replicated in Th1, Th2, and Th0 cells. In sharp contrast, CXCR4-dependent (X4) viruses poorly replicated in both polarized and unpolarized CD4(+) T cells, including adults' PBMC infected several days after mitogenic stimulation. Unlike the X4 HIV-1(NL4-3), a chimera in which the env gene had been replaced with that of the R5 HIV-1(NL(AD8)), efficiently replicated in both Th1 and Th2 cells. This X4-dependent restriction of HIV replication was not explained by either the absence of functional CXCR4 on the cell surface or by the inefficient viral entry and reverse transcription. T-cell receptor stimulation by anti-CD3 monoclonal antibodies fully rescued X4 HIV-1 replication in both Th1 and Th2 cells, whereas it did not alter the extent and kinetics of R5 HIV-1 spreading. Thus, R5 HIVs show a replicative advantage in comparison to X4 viruses in their ability to efficiently propagate among suboptimally activated T lymphocytes, regardless of their polarized or unpolarized functional profiles. This observation may help to explain the absolute predominance of R5 HIVs over X4 viruses observed after viral transmission and during early-stage disease.

Cutting edge: identification of novel T cell epitopes in Lol p5a by computational prediction

Although atopic allergy affects </=20% of the total population, the relationship between the protein structure and immunogenic activity of the allergens is still largely unknown. We observed that group 5 grass allergens are characterized by repeated structural motifs. Using a new algorithm, TEPITOPE, we predicted promiscuous HLA-DR ligands within the repeated motifs of the Lol p5a allergen from rye grass. In vitro binding studies confirmed the promiscuous binding characteristics of these peptides. Moreover, most of the predicted ligands were novel T cell epitopes that were able to stimulate T cells from atopic patients. We generated a panel of Lol p5a-specific T cell clones, the majority of which recognized the peptides in a cross-reactive fashion. The computational prediction of DR ligands might thus allow the design of T cell epitopes with potential useful application in novel immunotherapy strategies.

Regulation of the IL-12/IL-12R axis: a critical step in T-helper cell differentiation and effector function

Interleukin (IL)-12 is required for the development of T-helper (Th) 1 cells, which have been shown to be important for protective cell-mediated immune responses against a variety of intracellular pathogens. Recent studies have clarified the sources and the regulation of IL-12 production leading to Th1 development against microbes. Expression of IL-12R is necessary for maintaining IL-12 responsiveness and controlling Th1 lineage commitment. Advances in this area have included a broader understanding of the factors involved in the regulation of the IL-12R beta 2 signaling component. Expression of this receptor subunit in humans is critically influenced by IL-12 and type I interferons. IL-12 signaling results in STAT4 activation and interferon (IFN)-gamma production. Recent evidence suggests that IL-12 also modulates a number of genes involved in leukocyte trafficking. Thus, IL-12 is not only an important proinflammatory cytokine, which induces production of IFN-gamma and subsequent activation of phagocytic cells but also plays a major role in regulating the migration and proper positioning of effector cells.

Hydrolysis of NADP+ by platelet CD38 in the absence of synthesis and degradation of cyclic ADP-ribose 2'-phosphate

CD38 is a multifunctional cell surface ectoenzyme that catalyzes both the synthesis of cyclic ADP-ribose from NAD+ and its hydrolysis to ADP-ribose. In this work, we investigated the metabolism of NADP+ by CD38 expressed on human platelets. Incubation of either platelet membranes or intact cells with NADP+ resulted in the rapid and time-dependent accumulation of ADP-ribose 2'-phosphate that paralleled the consumption of the substrate. However, under the same conditions, synthesis of cyclic ADP-ribose 2'-phosphate was not observed. By immunoprecipitation experiments, we identified CD38 as the enzyme responsible for the observed NADP+ glycohydrolase activity. The lack of detection of cyclic ADP-ribose 2'-phosphate was not due to its rapid hydrolysis, since direct incubation of platelet membranes with cyclic ADP-ribose 2'-phosphate did not result in the formation of ADP-ribose 2'-phosphate. By contrast, the same membrane samples expressed a significant ability to hydrolyze cyclic ADP-ribose to ADP-ribose. The absence of cyclic ADP-ribose 2'-phosphate hydrolase activity was also confirmed using high concentrations of substrate and by analysing both intact Jurkat T-lymphocytes and immunoprecipitated CD38. These results indicate that CD38, which is a multifunctional enzyme towards NAD+, displays exclusively a NADP+ glycohydrolase activity and is unable to catalyze both the synthesis and the hydrolysis of cyclic ADP-ribose 2'-phosphate.

Peptidomimetic compounds that inhibit antigen presentation by autoimmune disease-associated class II major histocompatibility molecules

We have identified a heptapeptide with high affinity to rheumatoid arthritis-associated class II major histocompatibility (MHC) molecules. Using a model of its interaction with the class II binding site, a variety of mimetic substitutions were introduced into the peptide. Several unnatural amino acids and dipeptide mimetics were found to be appropriate substituents and could be combined into compounds with binding affinities comparable to that of the original peptide. Compounds were designed that were several hundred-fold to more than a thousand-fold more potent than the original peptide in inhibiting T-cell responses to processed protein antigens presented by the target MHC molecules. Peptidomimetic compounds of this type could find therapeutic use as MHC-selective antagonists of antigen presentation in the treatment of autoimmune diseases.

Generation of tissue-specific and promiscuous HLA ligand databases using DNA microarrays and virtual HLA class II matrices

Most pockets in the human leukocyte antigen-group DR (HLA-DR) groove are shaped by clusters of polymorphic residues and, thus, have distinct chemical and size characteristics in different HLA-DR alleles. Each HLA-DR pocket can be characterized by "pocket profiles," a quantitative representation of the interaction of all natural amino acid residues with a given pocket. In this report we demonstrate that pocket profiles are nearly independent of the remaining HLA-DR cleft. A small database of profiles was sufficient to generate a large number of HLA-DR matrices, representing the majority of human HLA-DR peptide-binding specificity. These virtual matrices were incorporated in software (TEPITOPE) capable of predicting promiscuous HLA class II ligands. This software, in combination with DNA microarray technology, has provided a new tool for the generation of comprehensive databases of candidate promiscuous T-cell epitopes in human disease tissues. First, DNA microarrays are used to reveal genes that are specifically expressed or upregulated in disease tissues. Second, the prediction software enables the scanning of these genes for promiscuous HLA-DR binding sites. In an example, we demonstrate that starting from nearly 20,000 genes, a database of candidate colon cancer-specific and promiscuous T-cell epitopes could be fully populated within a matter of days. Our approach has implications for the development of epitope-based vaccines.

Rap1B and Rap2B translocation to the cytoskeleton by von Willebrand factor involves FcgammaII receptor-mediated protein tyrosine phosphorylation

Stimulation of human platelets with von Willebrand factor (vWF) induced the translocation of the small GTPases Rap1B and Rap2B to the cytoskeleton. This effect was specifically prevented by an anti-glycoprotein Ib monoclonal antibody or by the omission of stirring, but was not affected by the peptide RGDS, which antagonizes binding of adhesive proteins to platelet integrins. Association of Rap2B with the cytoskeleton was very rapid, while translocation of Rap1B occurred in a later phase of platelet activation and was totally inhibited by cytochalasin D. vWF also induced the rapid tyrosine phosphorylation of several proteins that was prevented by the tyrosine kinases inhibitor genistein and by cAMP-increasing agents. Under these conditions, also the association of Rap1B and Rap2B with the cytoskeleton was prevented. Translocation of Rap proteins to the cytoskeleton induced by vWF, but not by thrombin, was inhibited by a monoclonal antibody against the FcgammaII receptor. The same antibody inhibited vWF-induced tyrosine phosphorylation of selected substrates with molecular masses of about 75, 95, and 150 kDa. Three of these substrates were identified as the tyrosine kinase pp72(syk), the phospholipase Cgamma2, and the inositol 5-phosphatase SHIP. Our results indicate that translocation of Rap1B and Rap2B to the cytoskeleton is regulated by tyrosine kinases and suggest a novel role for the FcgammaII receptor in the mechanism of platelet activation by vWF.

Antibodies to the IL-12 receptor beta 2 chain mark human Th1 but not Th2 cells in vitro and in vivo

Great attention has been placed on the possibility of distinguishing Th1 from Th2 cells on the basis of differential expression of surface receptors. We have recently shown that the differential expression of the IL-12R beta 2 chain in Th1 and Th2 cells, as measured at the mRNA level, accounts for an important regulatory mechanism in the differentiation of the two cell subsets. In this study, we identify IL-12R expression at the protein level. We have generated an anti-IL-12R beta 2-specific mAb and analyzed IL-12R beta 2 expression on polarized Th cell populations generated in vitro and on T cells derived from patients with Th1- or Th2-mediated inflammatory conditions. Although IL-12R beta 2 was absent in freshly isolated PBMC and in cord blood cells, we were able to detect IL-12R beta 2 expression selectively in differentiated Th1 and T cytotoxic 1, but not Th2 or T cytotoxic 2 cells. In the presence of IL-12, cell surface expression of the IL-12R beta 2 subunit was readily detected on T cells after 24 h, reached the maximum at day 5, and declined thereafter. Most importantly, the anti-IL-12R beta 2 mAb recognizes lung T cells from patients with sarcoidosis, a disease characterized by a typical cell-mediated, Th1-type inflammatory response. In contrast, IL-12R beta 2 was absent in lung T cells from patients with allergic asthma, a disease characterized by a Th2-type inflammatory response. The mAb reported in this study should represent a powerful tool to investigate the role of Th1 and Th2 cells in inflammatory conditions and to monitor therapies aimed at altering the balance of Th cell subsets.

Interleukin-12 induces expression of interferon regulatory factor-1 via signal transducer and activator of transcription-4 in human T helper type 1 cells

IRF-1-deficient mice show a striking defect in the development of T helper 1 (Th1) cells. In the present report, we investigate the expression of IRF-1 during differentiation of human T helper cells. No significant differences of IRF-1 mRNA expression were found in established Th1 and Th2 cells; however, interleukin 12 (IL-12) induced a strong up-regulation of IRF-1 transcripts in Th1 but not in Th2 cells. We demonstrate that IL-12-induced up-regulation of IRF-1 is mediated by signal transducer and activator of transcription-4, which binds to the interferon (IFN)-gamma-activated sequence present in the promoter of the IRF-1 gene. Strong IL-12-dependent activation of a reporter gene construct containing the IRF-1 IFN-gamma-activated sequence element provides further evidence for the key role of signal transducer and activator of transcription-4 in the IL-12-induced up-regulation of IRF-1 transcripts in T cells. IRF-1 expression was strongly induced after stimulation of naive CD4(+) T cells via the T cell receptor, irrespective of the cytokines present at priming, indicating that this transcription factor does not play a major role in initiating a Th1-specific transcriptional cascade in differentiating helper T cells. However, our finding that IRF-1 is a target gene of IL-12 suggests that some of the IL-12-induced effector functions of Th1 cells may be mediated by IRF-1.

Melanoma cells present a MAGE-3 epitope to CD4(+) cytotoxic T cells in association with histocompatibility leukocyte antigen DR11

In this study we used TEPITOPE, a new epitope prediction software, to identify sequence segments on the MAGE-3 protein with promiscuous binding to histocompatibility leukocyte antigen (HLA)-DR molecules. Synthetic peptides corresponding to the identified sequences were synthesized and used to propagate CD4(+) T cells from the blood of a healthy donor. CD4(+) T cells strongly recognized MAGE-3281-295 and, to a lesser extent, MAGE-3141-155 and MAGE-3146-160. Moreover, CD4(+) T cells proliferated in the presence of recombinant MAGE-3 after processing and presentation by autologous antigen presenting cells, demonstrating that the MAGE-3 epitopes recognized are naturally processed. CD4(+) T cells, mostly of the T helper 1 type, showed specific lytic activity against HLA-DR11/MAGE-3-positive melanoma cells. Cold target inhibition experiments demonstrated indeed that the CD4(+) T cells recognized MAGE-3281-295 in association with HLA-DR11 on melanoma cells. This is the first evidence that a tumor-specific shared antigen forms CD4(+) T cell epitopes. Furthermore, we validated the use of algorithms for the prediction of promiscuous CD4(+) T cell epitopes, thus opening the possibility of wide application to other tumor-associated antigens. These results have direct implications for cancer immunotherapy in the design of peptide-based vaccines with tumor-specific CD4(+) T cell epitopes.

Identification of destabilizing residues in HLA class II-selected bacteriophage display libraries edited by HLA-DM

HLA-DM (DM) functions as a peptide editor by catalyzing the release of class II-associated invariant chain peptides (CLIP) and other unstable peptides, thus supporting the formation of stable class II-peptide complexes for presentation. To investigate the general features that determine the DM susceptibility of HLA-DR1/peptide complexes, we generated a large DM-sensitive peptide repertoire from an M13 bacteriophage display library using a novel double selection protocol: we selected bacteriophage capable of binding to DR1 molecules and, subsequently, we enriched DR1-bound bacteriophage susceptible to elution by purified DM molecules. Sequence and mutational analyses of the DR1/DM double-selected peptides revealed that the amino acids Gly and Pro play a destabilizing role in the dissociation kinetics of DR1 ligands. This observation was confirmed also in natural peptide sequences such as CLIP 89-101, HA 307-319 and bovine collagen II (CII) 261-273. Our results demonstrate that DM susceptibility does not only depend on the number and nature of anchor residues, or the peptide length. Instead, less obvious sequence characteristics play a major role in the DM editing process and ultimately in the composition of peptide repertoires presented to T cells.

Clustering of integrin alphaIIb-beta3 differently regulates tyrosine phosphorylation of pp72syk, PLCgamma2 and pp125FAK in concanavalin A-stimulated platelets

Tyrosine phosphorylation of the non-receptor tyrosine kinases pp72syk and pp125FAK and of the gamma2 isoform of phospholipase C (PLCgamma2) in human platelets stimulated with the lectin Concanavalin A was investigated. Concanavalin A induced the rapid tyrosine phosphorylation of pp72syk and PLCgamma2 with a similar kinetics, while tyrosine phosphorylation of pp125FAK occurred in a later phase of platelet activation. When compared with other platelet agonists, Concanavalin A revealed to be at least as potent as collagen in inducing tyrosine phosphorylation of PLCgamma2 and pp125FAK, while tyrosine phosphorylation of pp72syk induced by the lectin was much stronger than that induced by thrombin or collagen. Concanavalin A-induced tyrosine phosphorylation of pp72syk, PLCgamma2 and pp125FAK was not dependent on platelet aggregation as it occurred normally even in the absence of sample stirring and when fibrinogen binding to integrin alphaIIb-beta3 was inhibited by the peptide RGDS. Tyrosine phosphorylation of pp72syk, PLCgamma2 and pp125FAK required the binding of the lectin to the platelet surface, but was not observed in platelets treated with succinyl-Concanavalin A, a derivative of the lectin that interacts with the same receptors but does not promote clustering of membrane glycoproteins. Moreover, the aggregation-independent tyrosine phosphorylation of pp125FAK and pp72syk induced by Concanavalin A required the expression of integrin alphaIIb-beta3 on the platelet surface as it was strongly inhibited in platelets from patients affected by Glanzmann thrombasthenia. By contrast, tyrosine phosphorylation of PLCalpha2 occurred normally also in thrombasthenic platelets stimulated with Concanavalin A. These results demonstrate that, even in the absence of aggregation, the clustering of integrin alphaIIb-beta3 induced by Concanavalin A on the platelet surface directly promotes tyrosine phosphorylation of pp72syk and pp125FAK and provide further evidence that the oligomerization of the fibrinogen receptor promoted by its natural ligand during platelet aggregation may be responsible for the tyrosine phosphorylation of these proteins induced by physiological agonists.

The role of Stat4 in species-specific regulation of Th cell development by type I IFNs

Type I IFNs (IFN-alpha/beta), in addition to IL-12, have been shown to play an important role in the differentiation of human, but not mouse, Th cells. We show here that IFN-alpha/beta act directly on human T cells to drive Th1 development, bypassing the need for IL-12-induced signaling, whereas IFN-alpha cannot substitute IL-12 for mouse Th1 development. The molecular basis for this species specificity is that IFN-alpha/beta activate Stat4 in differentiating human, but not mouse, Th cells. Unlike IL-12, which acts only on Th1 cells, IFN-alpha/beta can activate Stat4 not only in human Th1, but also in Th2 cells. However, restimulation of human Th2 lines and clones in the presence of IFN-alpha does not induce the production of IFN-gamma. These results suggest that activation of Stat4, which is necessary for the differentiation of naive T cells into polarized Th1 cells, is not sufficient to induce phenotype reversal of human Th2 cells.

The viral chemokine macrophage inflammatory protein-II is a selective Th2 chemoattractant

Kaposi's sarcoma (KS) lesions are characterized by a prominent leukocyte infiltrate composed of mononuclear phagocytes and T cells. KS-associated CD4(+) and CD8(+) cells showed predominantly a type II cytokine profile. The CC chemokine viral macrophage inflammatory protein-II (vMIP-II) encoded by the KS-associated herpes virus 8 was a selective chemoattractant for T helper 2 (Th2 cells) and for monocytes, whereas it was inactive on other leukocytes, including Th1 cells, dendritic cells, and natural killer (NK) cells. vMIP-II was an agonist for CCR8, a chemokine receptor selectively expressed on CD4(+) and CD8(+) cells with a type II cytokine profile. Hence, vMIP-II has agonist activity for a chemokine receptor (CCR8), which is preferentially expressed on polarized Th2 cells. The capacity of vMIP-II to attract type II T cells selectively is likely to be a component of the virus strategy to subvert the host immune response.

Selective up-regulation of chemokine receptors CCR4 and CCR8 upon activation of polarized human type 2 Th cells

Polarized Th1 and Th2 cells differentially express adhesion molecules and chemokine receptors, endowing these cells with distinct tissue homing capabilities. Here we report that, in contrast to other chemokine receptors, the expression of CCR4 and CCR8 on Th2 cells is transiently increased following TCR and CD28 engagement. IL-4 is not required for this activation-induced up-regulation of CCR4 and CCR8. In accordance with receptor expression, the response of Th2 cells to I-309 (CCR8 ligand) and thymus- and activation-regulated chemokine (CCR4 and CCR8 ligand) is enhanced upon activation. Moreover, activated Th1 cells up-regulate CCR4 expression and functional responsiveness to thymus- and activation-regulated chemokine. Analysis of polarized subsets of CD8+ T cells reveals a similar pattern of chemokine receptor expression and modulation of responsiveness. Taken together, these findings suggest that an up-regulation of CCR4 and CCR8 following Ag encounter may contribute to the proper positioning of activated T cells within sites of antigenic challenge and/or specialized areas of lymphoid tissues.

Decreased IL-12 production and Th1 cell development by acetyl salicylic acid-mediated inhibition of NF-kappaB

IL-12 is a 75-kDa heterodimeric cytokine composed of two covalently linked p35 and p40 chains. This pro-inflammatory cytokine plays a prominent role in the development of Th1 cell-mediated immune responses. Th1 cell-mediated immune responses have been implicated in the pathogenesis of chronic inflammatory autoimmune diseases. Thus, IL-12 appears to be a critical factor in the generation and maintenance of chronic inflammatory conditions. In this study, we investigated the effects of a commonly prescribed anti-inflammatory drug, acetyl salicylic acid (ASA), on IL-12 production and Th1 cell development. ASA was found to inhibit secretion of the IL-12 heterodimer as well as p40 monomer by human monocytic cells. This was associated with the down-regulation of IL-12p40 mRNA expression. Analysis of the regulation of the p40 gene promoter revealed that ASA inhibited NF-kappaB activation and binding to the p40-kappaB site in the p40 promoter, leading to transcriptional repression of the p40 gene. Addition of ASA to an in vitro T helper cell differentiation system, at concentrations compatible with plasma levels reached during anti-inflammatory therapy, resulted in reduced development of Th1 cells. These results suggest that the inhibition of NF-kappaB activation by ASA leads to down-regulation of IL-12 production and inhibition of Th1 cell development.

The chemokine receptor CCR8 is preferentially expressed in Th2 but not Th1 cells

In this paper we report on the cloning and characterization of mouse CCR8. Like its human homologue, it is predominantly expressed in the thymus. In the periphery, murine CCR8 mRNA was found most abundantly expressed in activated Th2-polarized cells and in NK1.1+ CD4+ T cells. Human CCR8 is also preferentially expressed in human Th2-polarized cells and clones. This pattern of expression suggests that CCR8 is part of a Th2-specific gene expression program. The CCR8 ligands I-309 and its mouse homologue T cell activation gene 3 (TCA-3) are potent chemoattractants for Th2-polarized cells. Taken together, these observations strongly suggest that CCR8 plays a role in the control of Th2 responses, and may represent a potential target for treatment of allergic diseases.