Invariant Natural Killer T cells resilience to paradoxical sleep deprivation-associated stress.

Although several studies demonstrate that stressful situations, such as sleep disturbances, negatively impact the innate and adaptive arms of the immune system, their influence on invariant Natural Killer T (iNKT) cells remains unclear. iNKT cells are CD1d-restricted innate T cells that recognize glycolipid antigens and rapidly produce polarizing cytokines being key players in several immune responses, and a potential target for immunotherapy. iNKT cells differ in several aspects from conventional T lymphocytes, including a unique dependence on CD1d-expressing double-positive (DP) thymocytes for intrathymic maturation. As a consequence of stress, DP thymocytes undergo glucocorticoid-induced apoptosis, which might compromise iNKT developmental pathway. Therefore, we used a paradoxical sleep deprivation (SD) model to determine the impact of sleep disturbance on iNKT cell biology. After 72 h of SD, C57Bl/6 mice exhibited a significant increase in systemic glucocorticoid levels and thymus atrophy. Despite marked decrease in the number of DP thymocytes, the ratio CD1d+/CD1d- was higher in SD mice, and the number of thymic iNKT cells remained unaltered, suggesting that SD did not compromise the iNKT developmental pathway. In contrast, SD reduced hepatic IFN-γ, but not, IL-4-producing iNKT cells, without further effect in the spleen. Despite this fact, SD did not affect stimulation of IFN-γ production by iNKT cells, or cytokine release, in response to α-galactosylceramide, a specific antigen. Furthermore, although SD impaired splenic NK cells activity against tumor cells, it did not affect iNKT cell-specific cytotoxicity. Thus, our study shows that SD-induced stress did not impair the iNKT cells' responses to a cognate antigen.

Neuroimmune interactions: dendritic cell modulation by the sympathetic nervous system.

Dendritic cells are of paramount importance bridging innate and adaptive immune responses. Depending on the context, after sensing environmental antigens, commensal microorganisms, pathogenic agents, or antigens from the diet, dendritic cells may drive either different effector adaptive immune responses or tolerance, avoiding tissue damage. Although the plasticity of the immune response and the capacity to regulate itself are considered essential to orchestrate appropriate physiological responses, it is known that the nervous system plays a relevant role controlling immune cell function. Dendritic cells present in the skin, the intestine, and lymphoid organs, besides expressing adrenergic receptors, can be reached by neurotransmitters released by sympathetic fibers innervating these tissues. These review focus on how neurotransmitters from the sympathetic nervous system can modulate dendritic cell function and how this may impact the immune response and immune-mediated disorders.

B-1 cells promote immunosurveillance against murine melanoma in host absence of CCR5: new perspective in autologous vaccination therapy.

Autologous vaccination with tumor-primed dendritic cells increases immune response against tumor, which seems to be improved in host absence of CCR5. Because B-1 lymphocytes modulate the activity of different immune cells, we decided to study their influence in the resistance against murine B16F10 melanoma in a CCR5 deprived environment. Adoptive transfer of peritoneal B-1 CCR5(+/+) lymphocytes to CCR5(-/-) animals inhibited the establishment of lung metastasis and melanoma cell growth, in comparison to saline-treated CCR5(-/-) mice. In loco cell analysis demonstrated that the adoptive transfer of B-1 CCR5(+/+) lymphocytes to CCR5 deficient host was associated with a more intense influx of T CD8(+) to tumor site, indicating that the presence of CCR5(+/+) B-1 cells in the tumor environment induces the migration of T CD8 CCR5(-/-) cells to the implantation site. To corroborate this idea, CCR5(-/-) mice were injected with non B-1 peritoneal cells from wild type (WT) mice before B16F10 inoculation. In this regimen, CCR5(-/-) mice were not protected from tumor growth reinforcing the idea that, in host absence of CCR5, B-1 cells are essential to confer tumor resistance. This work indicates that, in the host absence of CCR5, naive B-1 cells may activate CD8T lymphocytes thereby promoting tumor resistance. Our results strongly suggest that autologous vaccination with B-1 lymphocytes in combination with CCR5 antagonists can be an alternative approach to tumor therapy.

GCN2 kinase plays an important role triggering the remission phase of experimental autoimmune encephalomyelitis (EAE) in mice.

Experimental autoimmune encephalomyelitis (EAE) has been widely employed as a model to study multiple sclerosis (MS) and indeed has allowed some important advances in our comprehension of MS pathogenesis. Several pieces of evidence suggest that infiltrating Th1 and Th17 lymphocytes are important players leading to CNS demyelination and lesion during the peak of murine EAE. Subsequently, effector T cell responses rapidly decline and the recovery phase of the disease strongly correlates with the expression of anti-inflammatory cytokines and the enrichment of Foxp3+ regulatory T (Treg) cells within the target organ. However, the mechanisms leading to the increased presence of Treg cells and to the remission phase of the disease are still poorly understood. Recent researches demonstrated that chemically induced amino-acid starvation response might suppress CNS immune activity. Here we verified an important participation of the general control nonrepressible 2 (GCN2), a key regulator kinase of the amino-acid starvation response, in the development of the remission phase of EAE in C57BL/6 mice. By immunizing wild type C57BL/6 (WT) and GCN2 knock-out mice (GCN2 KO) with myelin oligodendrocyte glycoprotein peptide (MOG35-55), it was noticed that GCN2 KO mice did not develop the remission phase of the disease and this was associated with higher levels of CNS inflammation and increased presence of effector T cells (Th1/Th17). These animals also showed lower frequency of Treg cells within the CNS as compared to WT animals. Higher expression of indoleamine 2,3-dioxygenase (IDO) and higher frequency of plasmacytoid dendritic cells (pDCs) were found at the peak of the disease in the CNS of WT animals. Our results suggest that the GCN2 kinase-dependent sensing of IDO activity represents an important trigger to the EAE remission phase. The IDO-mediated immunoregulatory events may include the arresting of effector T cell responses and the differentiation/expansion of Treg cells within the target organ.

Beta2-adrenergic receptor signaling in CD4+ Foxp3+ regulatory T cells enhances their suppressive function in a PKA-dependent manner.

Beta2-adrenergic receptor (B2AR) signaling is known to impair Th1-cell differentiation and function in a cAMP-dependent way, leading to inhibition of cell proliferation and decreased production of IL-2 and IFN-γ. CD4(+) Foxp3(+) Treg cells play a key role in the regulation of immune responses and are essential for maintenance of self-tolerance. Nevertheless, very little is known about adrenergic receptor expression in Treg cells or the influence of noradrenaline on their function. Here we show that Foxp3(+) Treg cells express functional B2AR. B2AR activation in Treg cells leads to increased intracellular cAMP levels and to protein kinase A (PKA)-dependent CREB phosphorylation. We also found that signaling via B2AR enhances the in vitro suppressive activity of Treg cells. B2AR-mediated increase in Treg-cell suppressive function was associated with decreased IL-2 mRNA levels in responder CD4(+) T cells and improved Treg-cell-induced conversion of CD4(+) Foxp3(-) cells into Foxp3(+) induced Treg cells. Moreover, B2AR signaling increased CTLA-4 expression in Treg cells in a PKA-dependent way. Finally, we found that PKA inhibition totally prevented the B2AR-mediated increase in Treg-cell suppressive function. Our data suggest that sympathetic fibers are able to regulate Treg-cell suppressive activity in a positive manner through B2AR signaling.

Paracoccidioides brasiliensis GP43-derived peptides are potent modulators of local and systemic inflammatory response.

Paracoccidioidomycosis is a systemic granulomatous disease caused by the dimorphic fungus Paracoccidioides brasiliensis. Its major antigen is a 43 kDa glycoprotein whose peptides embody different functions: P10 peptide, a T-cell epitope, induces protective response while P4 and P23 peptides inhibit both, macrophage functions and inflammatory reaction, thus facilitating infection. Here we investigated the modulating mechanisms of the immune response exerted by P4 and P23 involved in the latter inhibitory effect on macrophages. Moreover we analyzed the peptides effects in different models in vivo. While evaluating whether P4 and P23 present systemic anti-inflammatory effects in vivo, we showed that their intraperitonial administration decreased footpad swelling in mice infected with either P. brasiliensis or Mycobacterium bovis. Both, qPCR and ELISA assays suggested that this anti-inflammatory effect depended on alterations in the kinetics of production of innate immunity modulators such as TNF-α, IL6, IL10 and TLR2. IL10 seems to be early produced than TNF-α and IL6, produced later in presence of peptides. Higher doses or intravenously given P4 and P23 resulted in earlier and more prolonged anti-inflammatory effects. Moreover, continuous treatment with P4 and P23 sustained the anti-inflammatory activity throughout.

Exercise Induced Alterations in Rat Monocyte Number, Morphology, and Function.

The purpose of this study was to verify the histophysiological alterations in monocytes and macrophages induced by short periods of exercise. Male Wistar rats (age = 2 months, body weight = 200g) were divided into seven groups (N = 6 each): sedentary control (C), groups exercised (swimming) at low intensity for 5 (5L), 10 (10L), and 15 minutes (15L), and groups exercised at moderate intensity for 5 (5M), 10 (10M) or 15 minutes (15M). At moderate intensity the animals carried a load of 5% of body weight on their backs. Blood monocytes were evaluated for quantity and morphology, and peritoneal macrophages were analyzed for quantity and phagocytic activity. Data were analyzed using ANOVA and Tukey's post hoc test (p ≤ 0.05). Low intensity groups and 5M exhibited an increase in monocyte levels when compared with the control. There was an increase in monocyte cellular area for the 5L, 10L, 5M and 10M groups; monocyte nuclear area increased for the 10L, 5M and 10M groups in comparison with the control. There was an increase in peritoneal macrophages for the 15L, 10M, 15M and decrease for the 5M group. Macrophage phagocytic capacity increased for low intensity groups and for 10M group. The exercise performed for short periods modulated macrophage levels and function, and monocyte levels and morphology, in an intensity-dependent manner. The sum of acute responses observed in this study may exert a protective effect against sickness and may be used to improve health and lifespan.