Ablation of the Cß2 subunit of PKA in immune cells leads to increased susceptibility to systemic inflammation in mice.

Protein kinase A (PKA) is a holoenzyme composed of a regulatory subunit dimer and two catalytic subunits and regulates numerous cellular functions including immune cell activity. There are two major catalytic subunit genes, PRKACA and PRKACB encoding the catalytic subunits Cα and Cß. The PRKACB gene encodes several splice variants including Cß2, which is enriched in T-, B- and natural killer cells. Cß2 is significantly larger (46 kDa) than any other C splice variant. In this study we characterized mice ablated for the Cß2 protein demonstrating a significantly reduced cAMP-induced catalytic activity of PKA in the spleenocytes, lymphocytes and thymocytes. We also observed a significantly increased number of CD62L-expressing CD4+ and CD8+ T cells in LNs, accompanied by increased susceptibility to systemic inflammation by the Cß2 ablated mice. The latter was reflected in an elevated sensitivity to collagen-induced arthritis (CIA), as well as higher concentration of TNF-α and lower concentration of IL-10 in response to LPS challenges. We suggest a role of Cß2 in regulating innate as well as adaptive immune sensitivity in vivo.

The 2011 Nobel Prize in physiology or medicine.

The 2011 Noble Prize in Physiology or Medicine was awarded to Bruce A. Beutler, Jules A. Hoffmann and Ralph M. Steinman for their groundbreaking research within immunology. Bruce A. Beutler and Jules A. Hoffmann were recognized for their discoveries on Toll and Toll-like receptor activation of innate immunity in fruit fly and mammals, respectively. Ralph M. Steinman received the award for the discovery of dendritic cells, a cell type bridging innate and adaptive immunity, and how these cells orchestrate immune responses.

Expression of heat shock protein 70 and NKG2D ligands in acute myeloid leukemia cell lines.

UNLABELLED: Membrane-bound heat shock protein 70 (HSP70) was found to be tumor-specific and was proposed as a target for immunotherapy. In the present study, we analyzed cell surface and relative gene expression of HSP70 in cell lines established from patients with different acute myeloid leukemia (AML) subtypes, together with the expression of natural killer (NK) cell activation/inhibitory ligands. MATERIALS AND METHODS: Six AML cell lines were included in this study. The relative gene expression of HSP70 was analyzed using the real-time reverse-transcriptase polymerase chain reaction. Surface expression of HSP70 and NK cell ligands was analyzed using flow cytometry. RESULTS: All cell lines overexpressed HSP70; however, its mRNA levels were not elevated. The expression of NKG2D activation ligands was heterogeneous. CONCLUSION: Our study is the first to describe long-term stationary cell surface expression of HSP70 in different subtypes of AML. Combined with the results of the gene expression experiments these data provide more evidence to the idea of a self-limiting mechanism for HSP70 expression.

Th17 Polarization under Hypoxia Results in Increased IL-10 Production in a Pathogen-Independent Manner.

The IL-17-producing CD4+ T helper cell (Th17) differentiation is affected by stimulation of the aryl hydrocarbon receptor (AhR) pathway and by hypoxia-inducible factor 1 alpha (HIF-1α). In some cases, Th17 become non-pathogenic and produce IL-10. However, the initiating events triggering this phenotype are yet to be fully understood. Here, we show that such cells may be differentiated at low oxygen and regardless of AhR ligand treatment such as cigarette smoke extract. Hypoxia led to marked alterations of the transcriptome of IL-10-producing Th17 cells affecting genes involved in metabolic, anti-apoptotic, cell cycle, and T cell functional pathways. Moreover, we show that oxygen regulates the expression of CD52, which is a cell surface protein that has been shown to suppress the activation of other T cells upon release. Taken together, these findings suggest a novel ability for Th17 cells to regulate immune responses in vivo in an oxygen-dependent fashion.

T Helper Cell Activation and Expansion Is Sensitive to Glutaminase Inhibition under Both Hypoxic and Normoxic Conditions.

Immune responses often take place where nutrients and O2 availability are limited. This has an impact on T cell metabolism and influences activation and effector functions. T cell proliferation and expansion are associated with increased consumption of glutamine which is needed in a number of metabolic pathways and regulate various physiological processes. The first step in endogenous glutamine metabolism is reversible and is regulated by glutaminase (GLS1 and GLS2) and glutamine synthase (GLUL). There are two isoforms of GLS1, Kidney type glutaminase (KGA) and Glutaminase C (GAC). The aim of this study is to investigate the expression, localization and role of GLS1 and GLUL in naïve and activated human CD4+ T cells stimulated through the CD3 and CD28 receptors under normoxia and hypoxia. In proliferating cells, GAC was upregulated and KGA was downregulated, and both enzymes were located to the mitochondria irrespective of O2 levels. By contrast GLUL is localized to the cytoplasm and was upregulated under hypoxia. Proliferation was dependent on glutamine consumption, as glutamine deprivation and GLS1 inhibition decreased proliferation and expression of CD25 and CD226, regardless of O2 availability. Again irrespective of O2, GLS1 inhibition decreased the proportion of CCR6 and CXCR3 expressing CD4+ T cells as well as cytokine production. We propose that systemic Th cell activation and expansion might be dependent on glutamine but not O2 availability.

In vitro suppression of immune responses using monocyte-derived tolerogenic dendritic cells from patients with primary Sjögren's syndrome.

INTRODUCTION: Therapeutic vaccination with antigen-specific tolerogenic dendritic cells (tolDC) might become a future option of individualized therapy for patients with autoimmune diseases. In this study, we tested the possibility of generating monocyte-derived tolDC from patients with primary Sjögren's syndrome (pSS). We analyzed phenotype, cytokine production and ability to suppress Ro/La-specific immune responses. METHODS: Monocyte-derived tolDC from patients with pSS were generated in the presence of dexamethasone, vitamin D3 and lipopolysaccharide (DexVD3 DC). The phenotype was analyzed by flow cytometry and the cytokine profile was investigated using a 25-plex Luminex assay and ELISA. The capacity to both stimulate Ro/La-specific T cells and suppress this response was evaluated by autologous mixed lymphocyte reaction (MLR). RESULTS: DC generated from patients with pSS had a similar phenotype and cytokine profile to those from healthy controls. DexVD3 DC from pSS patients induced little antigen-specific T cell proliferation, but DexVD3 DC-primed lymphocytes successfully suppressed Ro/La-specific T cell responses. CONCLUSIONS: DexVD3 DC presenting Ro/La antigens might be a promising new therapeutic option for patients with pSS.

The complexity of Sjögren's syndrome: novel aspects on pathogenesis.

In Sjögren's syndrome, like in most other autoimmune diseases, the enigma leading to a pathogenic attack against self has not yet been solved. By definition, the disease must be mediated by specific immune reactions against endogenous tissues to qualify as an autoimmune disease. In Sjögren's syndrome the autoimmune response is directed against the exocrine glands, which, as histopathological hallmark of the disease, display persistent and progressive focal mononuclear cell infiltrates. Clinically, the disease in most patients is manifested by two severe symptoms: dryness of the mouth (xerostomia) and the eyes (keratoconjunctivitis sicca). A number of systemic features have also been described and the presence of autoantibodies against the ubiquitously expressed ribonucleoprotein particles Ro (Sjögren's-syndrome-related antigen A - SSA) and La (SSB) further underline the systemic nature of Sjögren's syndrome. The original explanatory concept for the pathogenesis of Sjögren's syndrome proposed a specific, self-perpetuating, immune mediated loss of acinar and ductal cells as the principal cause of salivary gland hypofunction. Although straightforward and plausible, the hypothesis, however, falls short of accommodating several Sjögren's syndrome-related phenomena and experimental findings. Consequently, researchers considered immune-mediated salivary gland dysfunction prior to glandular destruction and atrophy as potential molecular mechanisms underlying the symptoms of dryness in Sjögren's syndrome. Accordingly, apoptosis, fibrosis and atrophy of the salivary glands would represent consequences of salivary gland hypofunction. The emergence of advanced bio-analytical platforms further enabled the identification of potential biomarkers with the intent to improve Sjögren's syndrome diagnosis, promote the development of prognostic tools for Sjögren's syndrome and the long-term goal to identify possible processes for therapeutic treatment interventions. In addition, such approaches allowed us to glimpse at the apparent complexity of Sjögren's syndrome.