The mechanisms that target class switch recombination (CSR) to antibody gene switch (S) regions are unknown. Analyses of switch site locations in wild-type mice and in mice that lack the Sμ tandem repeats show shifts indicating that a 4–5-kb DNA domain (bounded upstream by the Iμ promoter) is accessible for switching independent of Sμ sequences. This CSR-accessible domain is reminiscent of the promoter-defined domains that target somatic hypermutation. Within the 4–5-kb CSR domain, the targeting of S site locations also depends on the Msh2 mismatch repair protein because Msh2-deficient mice show an increased focus of sites to the Sμ tandem repeat region. We propose that Msh2 affects S site location because sequences with few activation-induced cytidine deaminase targets generate mostly switch DNA cleavages that require Msh2-directed processing to allow CSR joining.

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.

SummaryA 29-year-old female presented with intermittent nausea, vomiting, fevers, abdominal pain and fatigue. CT scans of the abdomen revealed inflammatory changes within the mesentery and small bowel. Histopathology of the mesentery and omentum showed chronic inflammation and fibrosis, supporting a diagnosis of sclerosing mesenteritis. Over the past 2 years, the patient suffered debilitating paroxysmal abdominal pain despite treatment with prednisone, azathioprine, sulfasalazine and narcotics. Additionally, she developed sacroiliitis diagnosed clinically and on radiographs. Intravenous infliximab (5 mg/kg intravenous) was initiated and continued every 6 weeks for 3 years. The patient has since had a dramatic improvement in her back and abdominal symptoms and has tapered off of prednisone, azathioprine and narcotics. Erythrocyte sedimentation rate, anaemia, leukocytosis and radiographic findings improved after initiation with infliximab. In conclusion, the authors report successfully treating sclerosing mesenteritis with sacroiliitis by the addition of infliximab. This may implicate a role for tumour necrosis factor α in disease pathogenesis. BACKGROUND

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