MDSCs are a heterogeneous group of myeloid cells that suppress T cell activity in cancer and autoimmune disease. The effect of MDSCs on B cell function is not clear. Using the CIA model of autoimmune disease, we found an increase in M-MDSCs in the periphery of WT mice with CIA compared with naïve mice. These MDSCs were absent from the periphery of CCR2(-/-) mice that developed exacerbated disease. M-MDSCs, isolated from immunized mice, inhibited autologous CD4(+) T cell proliferation. The M-MDSC-mediated suppression of T cell proliferation was NO and IFN-γ dependent but IL-17 independent. Furthermore, we demonstrated for the first time that M-MDSCs from CIA mice also inhibited autologous B cell proliferation and antibody production. The suppression of B cells by M-MDSCs was dependent on the production of NO and PGE2 and required cell-cell contact. Administration of M-MDSCs rescued CCR2(-/-) mice from the exacerbated CIA phenotype and ameliorated disease in WT mice. Furthermore, adoptive transfer of M-MDSCs reduced autoantibody production by CCR2(-/-) and WT mice. In summary, M-MDSCs inhibit T cell and B cell function in CIA and may serve as a therapeutic approach in the treatment of autoimmune arthritis.

Cell type-specific conditional activation of oncogenic K-Ras is a powerful tool for investigating the cell of origin of adenocarcinomas in the mouse lung. Our previous studies showed that K-Ras activation with a CC10(Scgb1a1)-CreER driver leads to adenocarcinoma in a subset of alveolar type II cells and hyperplasia in the bronchioalveolar duct region. However, no tumors develop in the bronchioles, although recombination occurs throughout this region. To explore underlying mechanisms, we simultaneously modulated either Notch signaling or Sox2 levels in the CC10+ cells along with activation of K-Ras. Inhibition of Notch strongly inhibits adenocarcinoma formation but promotes squamous hyperplasia in the alveoli. In contrast, activation of Notch leads to widespread Sox2+, Sox9+, and CC10+ papillary adenocarcinomas throughout the bronchioles. Chromatin immunoprecipitation demonstrates Sox2 binding to NOTCH1 and NOTCH2 regulatory regions. In transgenic mouse models, overexpression of Sox2 leads to a significant reduction of Notch1 and Notch2 transcripts, while a 50% reduction in Sox2 leads to widespread papillary adenocarcinoma in the bronchioles. Taken together, our data demonstrate that the cell of origin of K-Ras-induced tumors in the lung depends on levels of Sox2 expression affecting Notch signaling. In addition, the subtype of tumors arising from type II cells is determined in part by Notch activation or suppression.

CCR2 is considered a proinflammatory mediator in many inflammatory diseases such as rheumatoid arthritis. However, mice lacking CCR2 develop exacerbated collagen-induced arthritis. To explore the underlying mechanism, we investigated whether autoimmune-associated Th17 cells were involved in the pathogenesis of the severe phenotype of autoimmune arthritis. We found that Th17 cells were expanded approximately 3-fold in the draining lymph nodes of immunized CCR2−/− mice compared to WT controls (p = 0.017), whereas the number of Th1 cells and regulatory T cells are similar between these two groups of mice. Consistently, levels of the Th17 cell cytokine IL-17A and Th17 cell-associated cytokines, IL-6 and IL-1β were approximately 2–6-fold elevated in the serum and 22–28-fold increased in the arthritic joints in CCR2−/− mice compared to WT mice (p = 0.04, 0.0004, and 0.01 for IL-17, IL-6, and IL-1β, respectively, in the serum and p = 0.009, 0.02, and 0.02 in the joints). Furthermore, type II collagen-specific antibodies were significantly increased, which was accompanied by B cell and neutrophil expansion in CCR2−/− mice. Finally, treatment with an anti-IL-17A antibody modestly reduced the disease severity in CCR2−/− mice. Therefore, we conclude that while we detect markedly enhanced Th17-cell responses in collagen-induced arthritis in CCR2-deficient mice and IL-17A blockade does have an ameliorating effect, factors additional to Th17 cells and IL-17A also contribute to the severe autoimmune arthritis seen in CCR2 deficiency. CCR2 may have a protective role in the pathogenesis of autoimmune arthritis. Our data that monocytes were missing from the spleen while remained abundant in the bone marrow and joints of immunized CCR2−/− mice suggest that there is a potential link between CCR2-expressing monocytes and Th17 cells during autoimmunity.

Objective-Chemokine receptors are G-protein coupled receptors (GPCRs) phosphorylated by Gprotein receptor kinases (GRKs) after ligand-mediated activation. We hypothesized that GRK subtypes differentially regulate granulocyte chemotaxis and clinical disease expression in the K/BxN model. Methods-Clinical, histologic, and cytokine responses in GRK6−/−, GRK5−/−,GRK2+/−, and wildtype mice were evaluated using K/BxN serum transfer. Granulocyte chemotaxis was analyzed by transendothelial migration assays.Results-Both GRK6−/− and GRK2+/− mice had increased arthritis disease severity (p<0.001); whereas GRK5−/− was not different from controls. Acute weight loss was enhanced in GRK6−/− and GRK2+/− mice (p<0.001, days 3-10). However, GRK6−/− mice uniquely had more weight loss (>10%), elevated serum IL-6, and enhanced migration toward LTB4 and C5a in vitro.Conclusions-GRK6 and -2, but not GRK5,are involved in the pathogenesis of acute arthritis in the K/BxN model. In particular, GRK6 may dampen inflammatory responses by regulating granulocyte trafficking toward chemoattractants.G protein coupled receptors (GPCRs) are seven transmembrane spanning receptors that represent the largest superfamily of membrane-bound receptors in nature. With respect to immune function, GPCR-ligand interactions play critical roles in organ-specific leukocyte trafficking and activation, inflammatory-mediated chemotaxis, effector cell function, and cell survival [1;2]. Consequently, the regulation of GPCRs and their downstream signaling molecules are attractive therapeutic targets for patients with autoimmune disease.Correspondences and requests for reprints should be addressed to: Dr. Teresa Tarrant, MD, Assistant Professor of Medicine, University of North Carolina at Chapel Hill, CB# 7280, 3300 Manning Dr., Chapel Hill, NC 27599, tarra002@med.unc.edu. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. There are 7 different subtypes of GRKs [6] that have varying tissue distribution, suggesting some non-overlapping regulation of cellular functions. GRK1 and -7 are exclusively expressed in the retinal rods and cones respectively, and GRK4 has a high level of expression in the testes and a low level in kidney and cerebellum [7]. GRK subtypes -2, -3, -5, and -6 are expressed ubiquitously but have particularly high expression in leukocytes [8;9;10]. Moreover, GRK subtypes appear to be differently regulated in inflammatory disease states. Specifically, GRK6 and -2 protein levels are downregulated within peripheral blood mononuclear cells of rheumatoid arthritis patients [11]. In the rat model of adjuvant ar...

Objective CX3CR1 is a chemokine receptor that uniquely binds to its ligand fractalkine (FKN or CX3CL1) and has been shown to be important in inflammatory arthritis responses largely due to effects on cellular migration. In this study, we tested the hypothesis that genetic deficiency of CX3CR1 would be protective in the chronic inflammatory arthritis model, collagen induced arthritis (CIA). Because CX3CR1 is expressed on T cells and antigen-presenting cells, we additionally examined adaptive immune functions in this model. Methods Autoantibody formation, clinical, histologic, T cell proliferative, and cytokine responses were evaluated in DBA-1J mice deficient in (-/-) or wildtype (+/+) for CX3CR1 after immunization with heterologous type II collagen. Results CX3CR1-/- mice had an approximate 30% reduction in arthritis by two independent measures of paw swelling (p<0.01) and clinical disease score (p<0.0001). Additionally, CX3CR1-/- mice had an approximate 50% decrease in anti-type II collagen autoantibody formation (p<0.05), decreased Th17 intra-articular cytokine expression (IL-17 p<0.01 and IL-23 p<0.001), and decreased total numbers of Th17 cells in inflamed joints (p<0.05). Conclusions Deficiency of CX3CR1 is protective in inflammatory arthritis and may have effects that extend beyond migration that involve adaptive immune responses in autoimmune disease.