ICOS cooperates with CD28, IL-2, and IFN-g and modulates activation of human naïve CD4+ T cells

12 páginas, 7 figuras -- PAGS nros. 2601-2612Several sets of data indicate that ICOS regulates cytokine production in activated T cells, but is less effective on naïve T cells. This work evaluates ICOS function in human naïve CD4+ T cells through an assessment of the effect of soluble forms of the ICOS and CD28 physiological ligands on activation driven by anti-CD3 mAb. ICOS strikingly potentiated secretion of IL-2, IFN-γ, IL-10, and TNF-α, but not IL-4, promoted by optimal stimulation of CD3+CD28, and it was the key switching-factor of activation when cells received suboptimal stimulation of CD3+CD28 or stimulation of CD3 alone in the presence of exogenous IL-2. In these conditions, blockade of IL-2 and IFN-γ showed that ICOS builds up a positive feedback loop with IFN-γ, which required IL-2 and was inhibited by IL-4. By contrast, in the absence of CD28 triggering or exogenous IL-2, ICOS-induced costimulation mainly supported expression of TGF-β1 and FoxP3 and differentiation of regulatory T cells capable to inhibit proliferation of naïve CD4+ T cells driven by allogeneic cells. These data suggest that ICOS favors differentiation of Th effector cells when cooperates with appropriate activation stimuli such as CD3+CD28 or CD3+IL-2, whereas it supports differentiation of regulatory T cells when costimulatory signals are insufficientThis work was partially supported by Telethon grant E1170 (Rome), FISM grant 2003/R/20 (Genoa), PRIN Project (MIUR, Rome), Fondazione Cariplo (Milan), Compagnia di San Paolo (Turin), Fondazione Cassa di Risparmio di Cuneo (Cuneo), Regione Piemonte (Turin), and Associazione “Amici di Jean” (Turin)Peer reviewe

Altered expression of UVB-induced cytokines in human papillomavirus-immortalized epithelial cells

Keratinocytes can be induced to produce cytokines by exogenous stimuli, such as UVB, and dysregulation of this production has been described in various skin diseases, including cancer. In this study, we compared the effect of UVB on the secretion of several cytokines involved in inflammation by human keratinocytes immortalized or not with human papillomavirus (HPV)16 or HPV38 at the mRNA and protein levels. We show that expression of the HPV E6/E7 oncoproteins influences not only the basal cytokine secretion profile of keratinocytes, but also its modulation upon UVB irradiation. In particular, UVB upregulates interleukin (IL)-6, IL-8 and transforming growth factor (TGF)-β in HPV-immortalized cells to a higher extent than in control keratinocytes. Moreover, expression of other pro-inflammatory molecules such as S100A8/9 and interferon (IFN)-κ was downregulated in HPV-immortalized cells. These data support the functional similarity between HPV16 and 38, and suggest an active role of these viruses in modulation of the inflammatory process

Differential induction of IL-17, IL-10, and IL-9 in human T helper cells by B7h and B7.1.

ICOS and CD28 are expressed by T cells and are involved in costimulation of cytokine production in T helper (TH) cells. ICOS binds B7h expressed by several cell types, whereas CD28 binds B7.1 and B7.2 expressed by activated antigen presenting cells. This work investigated the role of B7h and B7.1 in TH17 and TH9 cell differentiation by assessing activity of recombinant B7h-Fc and B7.1-Fc on human na\uefve TH cells activated in the presence of different combinations of exogenous cytokines. In the presence of TGF-\u3b21 and IL-1\u3b2 (TH17 promoting condition), B7h-Fc was more effective than B7.1-Fc in inducing IL-17A and IL-10 secretion, whereas B7.1-Fc was more effective in inducing IL-17F. Dual costimulation with B7h-Fc and B7.1-Fc displayed an intermediate pattern with predominance of IL-17F over IL-17A, secretion of high levels of IL-10, and secretion of IL-9 levels lower than those induced by B7.1-Fc alone. In the presence of TGF-\u3b21 and IL-4 (TH9 promoting condition), B7h-Fc induced IL-17A only, whereas B7.1-Fc induced also IL-17F, IL-10, and high levels of IL-9. Experiments on memory TH cells showed that B7h-Fc mainly supported secretion of IL-17A and IL-10, whereas B7.1-Fc supported secretion of IL-17A, IL-17F, IL-10, and IL-9. These data indicate that B7h and B7.1 play different roles in modulation of TH17 and TH9 differentiation. This plasticity might be important in the immune response to pathogens and tumors, and in the development of autoimmune diseases, and should be taken in consideration in designing of immunotherapeutic protocols triggering ICOS or CD28

ICOS gene haplotypes correlate with IL10 secretion and multiple sclerosis evolution

6 páginas, 2 figuras, 3 tablas -- PAGS nros. 193-198Human ICOS is a T cell costimulatory molecule supporting IL10 secretion. A pilot study investigating variations of the ICOS gene 3'UTR detected 8 polymorphisms forming three haplotypes (A, B, C). Haplotype-A and -C displayed the highest difference. Activated T cells from healthy AA homozygotes expressed significantly less ICOS and secreted more IL10 than AC heterozygotes, whereas AB heterozygotes displayed intermediate levels. Analysis of 441 multiple sclerosis patients and 793 controls showed that frequency of AA homozygosity was significantly lower in MS patients with relapsing–remitting onset (N = 416) than in controls (OR = 0.70). Moreover, AA patients with relapsing–remitting onset had lower relapse rate and multiple sclerosis severity score than non-AA patientsThis work was partially supported by Telethon grant E1170 (Rome), FISM grant 2005/R/10 (Genoa), AIRC (Milan), PRIN Project (MIUR, Rome), Fondazione Cariplo (Milan), Compagnia di San Paolo (Turin), Fondazione Cassa di Risparmio di Cuneo (Cuneo), Regione Piemonte (Turin), and Associazione “Amici di Jean” (Turin)Peer reviewe

SAP-mediated inhibition of diacylglycerol kinase α regulates TCR-induced diacylglycerol signaling

Diacylglycerol kinases (DGKs) metabolize diacylglycerol to phosphatidic acid. In T lymphocytes, DGKα acts as a negative regulator of TCR signaling by decreasing diacylglycerol levels and inducing anergy. In this study, we show that upon costimulation of the TCR with CD28 or signaling lymphocyte activation molecule (SLAM), DGKα, but not DGKζ, exits from the nucleus and undergoes rapid negative regulation of its enzymatic activity. Inhibition of DGKα is dependent on the expression of SAP, an adaptor protein mutated in X-linked lymphoproliferative disease, which is essential for SLAM-mediated signaling and contributes to TCR/CD28-induced signaling and T cell activation. Accordingly, overexpression of SAP is sufficient to inhibit DGKα, whereas SAP mutants unable to bind either phospho-tyrosine residues or SH3 domain are ineffective. Moreover, phospholipase C activity and calcium, but not Src-family tyrosine kinases, are also required for negative regulation of DGKα. Finally, inhibition of DGKα in SAP-deficient cells partially rescues defective TCR/CD28 signaling, including Ras and ERK1/2 activation, protein kinase C membrane recruitment, induction of NF-AT transcriptional activity, and IL-2 production. Thus SAP-mediated inhibition of DGKα sustains diacylglycerol signaling, thereby regulating T cell activation, and it may represent a novel pharmacological strategy for X-linked lymphoproliferative disease treatment

Group I mGlu receptor stimulation inhibits activation-induced cell death of human T lymphocytes

1. The effects of L-glutamate on activation-induced cell death (AICD) of human activated (1 μg ml(−1) phytohemagglutinin plus 2 U ml(−1) interleukin-2; 8 days) T lymphocytes were studied by measuring anti-CD3 monoclonal antibody (10 μg ml(−1); 18 h)-induced cell apoptosis (Annexin V and propidium iodide staining). 2. L-Glutamate (1 × 10(−8)–1 × 10(−4) M) significantly (P⩽0.01) inhibited AICD in a concentration-dependent manner (EC(50)=6.3 × 10(−8) M; maximum inhibition 54.8±6.3% at 1 × 10(−6) M). 3. The L-glutamate inhibitory effect was pharmacologically characterized as mediated by group I mGlu receptors, since mGlu receptor agonists reproduced this effect. The EC(50) values were: 3.2 × 10(−7) M for (1S,3R)-ACPD; 4.5 × 10(−8) M for quisqualate; 1.0 × 10(−6) M for (S)-3,5-DHPG; 2.0 × 10(−5) M for CHPG. 4. Group I mGlu receptor antagonists inhibited the effects of quisqualate 1.0 × 10(−6) M. The IC(50) values calculated were: 8.7 × 10(−5), 4.3 × 10(−6) and 6.3 × 10(−7) M for AIDA, LY 367385 and MPEP, respectively. 5. L-Glutamate (1 × 10(−6) M; 18 h) significantly (P⩽0.05) inhibited FasL expression (40.8±11.3%) (cytofluorimetric analysis), whereas it did not affect Fas signalling. 6. Expression of both mGlu(1) and mGlu(5) receptor mRNA by T lymphocytes and T-cell lines, as demonstrated by reverse transcriptase–PCR analysis, suggests that L-glutamate-mediated inhibition of AICD was exerted on T cells. 7. These data depict a novel role for L-glutamate in the regulation of the immune response through group I mGlu receptor-mediated mechanisms