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HDLs appear to affect regulatory T cell (Treg) homeostasis, as suggested by the increased Treg counts in HDL-treated mice and by the positive correlation between Treg frequency and HDL-cholesterol levels in statin-treated healthy adults. However, the underlying mechanisms remain unclear. Herein, we show that HDLs, not LDLs, significantly decreased the apoptosis of human Tregs in vitro, whereas they did not alter naïve or memory CD4+T cell survival. Sim- ilarly, oleic acid bound to serum albumin increased Treg sur- vival. Tregs bound and internalized high amounts of HDL compared with other subsets, which might arise from the higher expression of the scavenger receptor class B type I by Tregs; accordingly, blocking this receptor hindered HDL- mediated Treg survival. Mechanistically, we showed that HDL increased Treg ATP concentration and mitochondrial activity, enhancing basal respiration, maximal respiration, and spare respiratory capacity. Blockade of FA oxidation by etoxomir abolished the HDL-mediated enhanced survival and mitochondrial activity. Our findings thus suggest that Tregs can specifically internalize HDLs from their microenvironment and use them as an energy source. Furthermore, a novel implication of our data is that enhanced Treg survival may contribute to HDLs’ anti-inflammatory properties. COL0012444

Summary Regulatory T cells (Tregs) modulate the magnitude of immune responses and possess therapeutic potential in an array of immune diseases. Statins reduce the activation and proliferation of conventional T cells (Tcons), and they seem to up-regulate the frequency and function of Tregs. However, there is a lack of simultaneous evaluation of the in-vitro effect of statins on the functional profile of Tregs versus Tcons. Herein, magnetically purified Tcons and Tregs were stimulated with CD3/CD28/interleukin (IL)-2 in the presence of atorvastatin (ATV) at 1 or 10 µM. The suppressive function of Tregs, the expression of markers associated with Treg function, activation levels, cytokine production and calcium flux in both subpopulations were assessed by flow cytometry. ATV had no cytotoxic effect on T cells at the concentrations used. Interestingly, 10 µM ATV hampered the suppressive capacity of Tregs. Moreover, this higher concentration reduced the expression of forkhead box protein 3 (FoxP3), cytotoxic T lymphocyte antigen (CTLA-4) and programmed death 1 (PD-1). In Tcons, ATV at 10 µM decreased PD-1 and CD45RO expression. The expression of CD25, CD69, CD95, CD38, CD62L, CCR7 and perforin was not affected in both subpopulations or at any ATV concentrations. Remarkably, 10 µM ATV increased the percentage of tumour necrosis factor (TNF)-α-producing Tregs. Although there was a reduction of calcium flux in Tcons and Tregs, it was only significant in 10 µM ATV-treated Tcons. These results suggested that 10 µM ATV affects the cellular functions of both populations; however, this concentration particularly affected several aspects of Treg biology: its suppressive function, cytokine production and expression of Treg-specific markers.

Summary Regulatory T cells (Tregs) constitute a fascinating subpopulation of CD4+ T cells due to their ability to limit the immune response against self and non-self antigens. Murine models and antibodies directed against surface and intracellular molecules have allowed elucidation of the mechanisms that govern their development and function. However, these markers used to their classification lack of specificity, as they can be expressed by activated T cells. Similarly, there are slight differences between animal models, in steady state and pathological conditions, anatomical localization and strategy of analysis by flow cytometry. Here, we revised the most common markers utilized for Treg typification by flow cytometry such as CD25, forkhead box protein 3 (FoxP3) and CD127, along with our data obtained in different body compartments of humans, mice and rats. Furthermore, we revised and determined the expression of other molecules important for the phenotypical characterization of Treg cells. We draw attention to the drawbacks of those markers used in chronic states of inflammation. However, until a specific marker for the identification of Tregs is discovered, the best combination of markers will depend upon the tissue or the degree of inflammation from which Tregs derive.

Objective: To evaluate the role of regulatory T cells (Tregs) at late stages of stroke. Methods: Anti-CD25 antibody (or PBS as a control) was injected to reduce the pool of Tregs in Wistar rats; then, ischemia was induced transiently by middle cerebral artery occlusion during 60 min and reperfusion was allowed for 7 d. Then, Treg frequency was analyzed in peripheral blood, spleen and lymph nodes. Neurological score (0-6) and infarct volume were also determined. Results: Nine days after injection, the CD4+ CD25+ T cells were reduced by 70.4%, 44.8% and 57.9% in peripheral blood, spleen and lymph nodes, respectively compared to PBS-treated rats. In contrast, the reduction of CD4+ FOXP3+ T cells was lower in the same compartments (38.6%, 12.5%, and 29.5%, respectively). The strongest reduction of CD25+ CD4+ T cells was observed in those FOXP3-negative cells in blood, spleen and lymph nodes (77.8%, 52.8%, and 60.7%, respectively), most likely corresponding to activated T cells. Anti-CD25-treated transient middle cerebral artery occlusion rats had a lower neurological deficit and did not develop tissue damage compared with PBS-treated animals. Conclusions: These findings suggest that treatment with anti-CD25 in our model preferentially reduce the T cell population with an activated phenotype, rather than the Treg population, leading to neuroprotection by suppressing the pathogenic response of effector T cells. COL0070457 COL0012444 COL0010744 COL0008639

RESUMEN: Las estatinas se han demostrado para modular el número y la función supresora de células T CD4 + FOXP3 (Treg) en condiciones inflamatorias. Sin embargo, no está bien establecido si estatinas también podría afectar Treg en ausencia de inflamación. Para abordar esta cuestión, dieciocho sujetos masculinos normocolesterolémicos fueron tratados con lovastatina o atorvastatina al día durante 45 días. La frecuencia y el fenotipo de circulación Treg se evaluaron en los días 0, 7, 30, y 45. Los niveles de ARNm de FOXP3, IDO, TGF-β, e IL-10 se midieron en las células T CD4 +. Se encontró que tanto los que aumenta significativamente los niveles de ARNm y de frecuencia de Treg FOXP3 en el día 30. En el día 45, los números de Treg volvieron a los valores basales; Sin embargo, el TGF-β y los niveles de ARNm de FOXP3 se mantuvo alta, acompañada por el aumento de los porcentajes de CTLA-4 y GITR que expresan Treg. Treg expresión de Ki-67 se redujo tras el tratamiento con estatinas. la frecuencia de Treg correlacionó positivamente con los niveles plasmáticos de colesterol de lipoproteínas de alta densidad (HDL-C), lo que sugiere un papel para el HDL-C en la homeostasis de Treg. Por lo tanto, las estatinas parecen tener efectos inmunomoduladores inflamación independiente. Por lo tanto, el aumento de la frecuencia de Treg células probablemente contribuye a inmunomoduladores efecto de las estatinas, incluso en individuos sanos. ABSTRACT: Statins have been shown to modulate the number and the suppressive function of CD4+FOXP3+ T cells (Treg) in inflammatory conditions. However, it is not well established whether statin could also affect Treg in absence of inflammation. To address this question, eighteen normocholesterolemic male subjects were treated with lovastatin or atorvastatin daily for 45 days. The frequency and phenotype of circulating Treg were evaluated at days 0, 7, 30, and 45. mRNA levels of FOXP3, IDO, TGF-β, and IL-10 were measured in CD4+ T cells. We found that both statins significantly increased Treg frequency and FOXP3 mRNA levels at day 30. At day 45, Treg numbers returned to baseline values; however, TGF-β and FOXP3 mRNA levels remained high, accompanied by increased percentages of CTLA-4- and GITR-expressing Treg. Treg Ki-67 expression was decreased upon statin treatment. Treg frequency positively correlated with plasma levels of high-density lipoprotein cholesterol (HDL-c), suggesting a role for HDL-c in Treg homeostasis. Therefore, statins appear to have inflammation-independent immune-modulatory effects. Thus, the increase in Treg cells frequency likely contributes to immunomodulatory effect of statins, even in healthy individuals