Conclusion. These data suggest that IL-22, produced by synovial fibroblasts and macrophages, promotes inflammatory responses in RA synovial tissues by inducing the proliferation and chemokine production of synovial fibroblasts.

Src homology 2 domain-containing protein tyrosine phosphatase (SHP) substrate-1 (SHPS-1) is a transmembrane protein that is expressed predominantly in macrophages. Its extracellular region interacts with the transmembrane ligand CD47 expressed on the surface of adjacent cells, and its cytoplasmic region binds the protein tyrosine phosphatases SHP-1 and SHP-2. Phagocytosis of IgG- or complement-opsonized RBCs by peritoneal macrophages derived from mice that express a mutant SHPS-1 protein that lacks most of the cytoplasmic region was markedly enhanced compared with that apparent with wild-type macrophages. This effect was not observed either with CD47-deficient RBCs as the phagocytic target or in the presence of blocking Abs to SHPS-1. Depletion of SHPS-1 from wild-type macrophages by RNA interference also promoted FcγR-mediated phagocytosis of wild-type RBCs. Ligation of SHPS-1 on macrophages by CD47 on RBCs promoted tyrosine phosphorylation of SHPS-1 and its association with SHP-1, whereas tyrosine phosphorylation of SHPS-1 was markedly reduced in response to cross-linking of FcγRs. Treatment with inhibitors of PI3K or of Syk, but not with those of MEK or Src family kinases, abolished the enhancement of FcγR-mediated phagocytosis apparent in macrophages from SHPS-1 mutant mice. In contrast, FcγR-mediated tyrosine phosphorylation of Syk, Cbl, or the γ subunit of FcR was similar in macrophages from wild-type and SHPS-1 mutant mice. These results suggest that ligation of SHPS-1 on macrophages by CD47 promotes the tyrosine phosphorylation of SHPS-1 and thereby prevents the FcγR-mediated disruption of the SHPS-1-SHP-1 complex, resulting in inhibition of phagocytosis. The inhibition of phagocytosis by the SHPS-1-SHP-1 complex may be mediated at the level of Syk or PI3K signaling.

IntroductionThe lifespan of circulating red blood cells (RBCs) is approximately 120 and 40 days in humans and mice, respectively, and is determined by their production in bone marrow (BM) and their clearance from the peripheral circulation, predominantly in the spleen and liver. [1][2][3] The production of RBCs is controlled by the primary erythropoietic regulator erythropoietin, 2,4 whereas clearance of old RBCs by the spleen is achieved mostly as a result of their specific recognition and phagocytosis by splenic macrophages. 5,6 The precise molecular mechanism by which splenic macrophages recognize senescent RBCs for phagocytosis is largely unknown, however. [1][2][3] Src homology 2 domain-containing protein tyrosine phosphatase substrate-1 (SHPS-1), 7,8 also known as signal-regulatory protein ␣, 9 brain immunoglobulin (Ig)-like molecule with tyrosinebased activation motifs, 10 and p84 neural adhesion molecule, 11 is a transmembrane protein that is especially abundant in macrophages. [12][13][14] The putative extracellular region of SHPS-1 comprises 3 Ig-like domains, and its cytoplasmic region contains 4 tyrosine phosphorylation sites that mediate the binding of Src homology 2 domain-containing protein tyrosine phosphatases designated SHP-1 and SHP-2. 7,9 Tyrosine phosphorylation of SHPS-1 is regulated by various growth factors and cytokines as well as by integrinmediated cell adhesion to extracellular matrix proteins. 7,9,[15][16][17][18] SHPS-1 thus functions as a docking protein to recruit and activate SHP-1 or SHP-2 at the cell membrane in response to extracellular stimuli. In macrophages, tyrosine-phosphorylated SHPS-1 binds SHP-1, 12,19,20 which is implicated in negative regulation of the functions of a variety of hematopoietic cells. [21][22][23] The complex of SHPS-1 and SHP-1 is thus thought to regulate macrophage functions in a negative manner.CD47 is a ligand for the extracellular region of SHPS-1. 24,25 This protein, which was originally identified in association with ␣v␤3 integrin, is also a member of the Ig superfamily, possessing an Ig-V-like extracellular domain, 5 putative membrane-spanning segments, and a short cytoplasmic tail. 26 CD47 and SHPS-1 constitute a cell-cell communication system (the CD47-SHPS-1 system) that plays important roles in a variety of cellular processes including cell migration, 27,28 adhesion of B cells, 29 and T-cell activation. 14,30 In addition, the CD47-SHPS-1 system is implicated in negative regulation of phagocytosis by macrophages. CD47 is highly expressed on the surface of RBCs, where it associates with the Rh protein complex instead of with integrins. 31 The rate of clearance of CD47-deficient RBCs from the bloodstream was found to be markedly increased compared with that of wild-type (WT) cells. 6,32 Furthermore, the phagocytosis of CD47-deficient RBCs by splenic or BM-derived macrophages was greatly enhanced Supported by a Grant-in-Aid for Scientific Research on Priority Areas Cancer; a Grant-in-Aid for Scientific Research (B); a Grant-in-Aid for Young Scie...

Chronic immune thrombocytopenic purpura (ITP) is an autoimmune disorder characterized by increased platelet clearance because of antiplatelet antibodies. It was recently reported that the balance of T helper 1 (Th1) and T helper 2 (Th2) subsets has been implicated in the regulation of many immune responses. In this study, the intracellular interleukin-4 and interferon-gamma production in CD4+ T-lymphocytes activated by phorbol 12-myristate 13-acetate and ionomycin was assessed via flow cytometry in order to determine the clinical significance of the Th1/Th2 ratio in 42 patients with ITP. The study cohort included 28 untreated patients, seven postprednisolone therapy patients and seven postsplenectomy patients. The mean level of the Th1/Th2 ratio in the untreated group was 36.9 (95% CI 25.8-47.9), and significantly higher than in the control group (mean 12.8, 95% CI 9.5-16.1). The mean levels of the Th1/Th2 ratio in the postprednisolone therapy and postsplenectomy groups were 20.5 (95% CI 8.4-32.6) and 16.4 (95% CI 3.1-29.7), respectively, but were no significant differences as compared with control subjects. When untreated patients were divided into two subgroups by Th1/Th2 ratio, the mean level of platelet associated IgG in the high Th1/Th2 subgroup (higher than upper limit of control group) tended to be higher than in the normal Th1/Th2 subgroup. In conclusion, the high Th1/Th2 ratio was closely related to the etiology and disease status of chronic ITP.

Sulfite, which is known as a major constituent of volcanic gas, is endogenously produced in mammals, and its concentration in serum is increased in patients with pneumonia. It has been reported that sulfite is produced by oxidation from hydrogen sulfide (H2S) as an intermediate in the mammalian body. The objective of this study was to investigate the ability of reactive oxygen species from neutrophils to produce sulfite from H2S. Sulfite production from activated neutrophils stimulated with N-formyl-methionyl-leucyl-phenylalanine gradually increased with an increased concentration of sodium hydrosulfide (NaHS) in the medium. The production of sulfite was markedly suppressed with an NADPH oxidase inhibitor, diphenyleneiodonium. When NaHS was added to the supernatant of activated neutrophils, a significant amount of sulfite was synthesized in the test tubes. Furthermore, when a medium containing NaHS was incubated with a water-soluble radical initiator, 2,2'-azobis-(amidinopropane) dihydrochloride, sulfite was formed in the solution and this increase was markedly suppressed by ascorbic acid. Finally, we determined serum concentrations of sulfite and H2S in an in vivo model of neutrophil activation induced by systemic injection of lipopolysaccharide (LPS) into rats. We found a significant increase in serum sulfite and H2S after LPS injection. Importantly, coadministration of ascorbic acid with LPS further increased serum H2S but suppressed sulfite levels. This finding implies that oxidative stress-dependent conversion of H2S to sulfite might occur in vivo. Thus, the oxidation of H2S is a novel sulfite production pathway in the inflammatory condition, and this chemical synthesis might be responsible for the upregulation of sulfite production in inflammatory conditions such as pneumonia.

The molecular basis for regulation of dendritic cell (DC) development and homeostasis remains unclear. Signal regulatory protein α (SIRPα), an immunoglobulin superfamily protein that is predominantly expressed in DCs, mediates cell-cell signaling by interacting with CD47, another immunoglobulin superfamily protein. We now show that the number of CD11c(high) DCs (conventional DCs, or cDCs), in particular, that of CD8-CD4+ (CD4+) cDCs, is selectively reduced in secondary lymphoid tissues of mice expressing a mutant form of SIRPα that lacks the cytoplasmic region. We also found that SIRPα is required intrinsically within cDCs or DC precursors for the homeostasis of splenic CD4+ cDCs. Differentiation of bone marrow cells from SIRPα mutant mice into DCs induced by either macrophage-granulocyte colony-stimulating factor or Flt3 ligand in vitro was not impaired. Although the accumulation of the immediate precursors of cDCs in the spleen was also not impaired, the half-life of newly generated splenic CD4+ cDCs was markedly reduced in SIRPα mutant mice. Both hematopoietic and nonhematopoietic CD47 was found to be required for the homeostasis of CD4+ cDCs and CD8-CD4- (double negative) cDCs in the spleen. SIRPα as well as its ligand, CD47, are thus important for the homeostasis of CD4+ cDCs or double negative cDCs in lymphoid tissues.

This study showed that in Class IV-G cases, renal outcome differed in the presence of chronicity. Chronicity could be a critical factor in predicting outcome. Thus, the revised classification of LN is clinically valuable in identifying different renal outcomes among patients with diffuse LN.

Src homology 2 domain-containing protein tyrosine phosphatase (SHP) substrate-1 (SHPS-1) is a transmembrane protein that binds the protein tyrosine phosphatases SHP-1 and SHP-2 through its cytoplasmic region and is expressed on the surface of CD11c+ dendritic cells (DCs) and macrophages. In this study, we show that mice that express a mutant form of SHPS-1 lacking most of the cytoplasmic region are resistant to experimental autoimmune encephalomyelitis (EAE) in response to immunization with a peptide derived from myelin oligodendrocyte glycoprotein (MOG (35–55)). The MOG (35–55)-induced proliferation of, and production of IFN-γ, IL-2, and IL-17, by T cells from immunized SHPS-1 mutant mice were reduced compared with those apparent for wild-type cells. The abilities of splenic DCs from mutant mice to stimulate an allogenic MLR and to prime Ag-specific T cells were reduced. Both IL-12-stimulated and TLR-dependent cytokine production by DCs of mutant mice were also impaired. Finally, SHPS-1 mutant mice were resistant to induction of EAE by adoptive transfer of MOG (35–55)-specific T cells. These results show that SHPS-1 on DCs is essential for priming of naive T cells and the development of EAE. SHPS-1 is thus a potential therapeutic target in inflammatory disorders of the CNS and other autoimmune diseases.