Thymic stromal lymphopoietin (TSLP) is an IL-7–related cytokine, produced by epithelial cells, that has been linked to atopic dermatitis and asthma; however, it remains unclear how TSLP shapes the adaptive immune response that causes these allergic disorders. In this study, we demonstrate a role for TSLP in a Th2 model of contact hypersensitivity in mice. TSLP is required for the development of Th2-type contact hypersensitivity induced by the hapten FITC in combination with the sensitizing agent dibutyl phthalate. TSLPR-deficient mice exhibited a dramatically reduced response, including markedly reduced local infiltration by eosinophils, Th2 cytokine production, and serum IgE levels, following FITC sensitization and challenge. The reduced response by TSLPR-deficient mice is likely due to decreased frequency and reduced T cell stimulatory function of skin-derived Ag-bearing FITC+CD11c+ dendritic cells in draining lymph nodes following FITC sensitization. These data suggest that skin-derived dendritic cells are direct or indirect targets of TSLP in the development of type 2 immune responses in the skin, where TSLP drives their maturation, accumulation in skin draining lymph nodes, and ability to induce proliferation of naive allergen-specific T cells.

The cytokine thymic stromal lymphopoietin (TSLP) drives immature B cell development in vitro and may regulate T helper type 2 responses. Here we analyzed the involvement of TSLP in B cell development in vivo with a doxycycline-inducible, keratin 5-driven transgene encoding TSLP (K5-TSLP). K5-TSLP-transgenic mice given doxycycline showed an influx of immature B cells into the periphery, with population expansion of follicular mature B cells, near-complete loss of marginal zone and marginal zone precursor B cells, and 'preferential' population expansion of peritoneal B-1b B cells. These changes promoted cryoglobulin production and immune complex-mediated renal disease. Identical events occurred in mice without T cells, in alternative TSLP-transgenic models and in K5-TSLP-transgenic mice with undetectable systemic TSLP. These observations suggest that signals mediating localized TSLP expression may modulate systemic B cell development and promote humoral autoimmunity.

A tyrosine kinase adaptor protein containing pleckstrin homology and SH2 domains (APS) is rapidly and strongly tyrosine phosphorylated by insulin receptor kinase upon insulin stimulation. The function of APS in insulin signaling has heretofore remained unknown. APS-deficient (APS ؊/؊ ) mice were used to investigate its function in vivo. The blood glucose-lowering effect of insulin, as assessed by the intraperitoneal insulin tolerance test, was increased in APS ؊/؊ mice. Plasma insulin levels during fasting and in the intraperitoneal glucose tolerance test were lower in APS ؊/؊ mice. APS ؊/؊ mice showed an increase in the whole-body glucose infusion rate as assessed by the hyperinsulinemic-euglycemic clamp test. These findings indicated that APS ؊/؊ mice exhibited increased sensitivity to insulin. However, overexpression of wild-type or dominant-negative APS in 3T3L1 adipocytes did not affect insulin receptor numbers, phosphorylations of insulin receptor, insulin receptor substrate-1, or Akt and mitogen-activated protein kinase. The glucose uptake and GLUT4 translocation were not affected by insulin stimulation in these cells. Nevertheless, the insulin-stimulated glucose transport in isolated adipocytes of APS ؊/؊ mice was increased over that of APS ؉/؉ mice. APS ؊/؊ mice also showed increased serum levels of leptin and adiponectin, which might explain the increased insulin sensitivity of adipocytes. Diabetes 52: [2657][2658][2659][2660][2661][2662][2663][2664][2665] 2003 I nsulin signaling begins with the binding of insulin to its receptor present on the cell surface, and activation of the insulin receptor tyrosine kinase results in tyrosine phosphorylation of a number of intracellular substrates. These molecules, including the insulin receptor substrate (IRS) family (1), src homology and collagen (2), Gab1 (3), and Grb10 (4), act as adaptor molecules that link between the insulin receptor and downstream signaling effectors. Adaptor protein containing a pleckstrin homology and SH2 domain (APS) is also one of the substrates that tyrosine phosphorylated by insulin receptor kinase (5,6).APS was first described to interact with an oncogenic mutant of the tyrosine kinase receptor c-Kit (7), and APS was isolated by the two-hybrid system using the cytoplasmic domain of the human insulin receptor as bait (5,6). APS (66.5 kDa) forms an adaptor protein family together with Lnk (8,9) and SH2-B (SH2-B␣, SH2-B␤, SH2-B␥, and SH2-B␦) (10 -13), whose members share a homologous NH 2 -terminal region with proline-rich stretches, pleckstrin homology and SH2 domains, and a conserved COOHterminal tyrosine phosphorylation site. It has been demonstrated that some members of this adaptor protein family act as modulators of signaling through various tyrosine kinase receptors. Lnk plays a role in regulating production of B-cell precursors and hematopoietic progenitor cells (8,14). SH2-B is an important signaling molecule in the insulin-like growth factor I (IGF-1) mediated reproductive pathway (13).APS is highly expressed in insulin-r...

SH2-B and APS, two members of a pleckstrin homology and SH2 domain-containing adaptor family, promote both insulin and leptin signaling in a similar fashion in cultured cells. In addition, APS mediates insulin-stimulated activation of the c-Cbl/CAP/TC10 pathway in cultured adipocytes. Here we characterized genetically modified mice lacking SH2-B, APS, or both to determine the physiological roles of these two proteins in animals. Disruption of the SH2-B gene resulted in obesity, hyperglycemia, hyperinsulinemia, and glucose intolerance. Conversely, deletion of the APS gene did not alter adiposity, energy balance, and glucose metabolism. Energy intake, energy expenditure, fat content, body weight, and plasma insulin, leptin, glucose, and lipid levels were similar between APS(-/-) and WT littermates fed either normal chow or a high-fat diet. Moreover, deletion of APS failed to alter insulin and glucose tolerance. APS(-/-)/SH2-B(-/-) double knockout mice also developed energy imbalance, obesity, hyperleptinemia, hyperinsulinemia, hyperglycemia, and glucose intolerance; however, plasma leptin and insulin levels were significantly lower in APS(-/-)/SH2-B(-/-) than in SH2-B(-/-) mice. These results suggest that SH2-B, but not APS, is a key positive regulator of energy and glucose metabolism in mice.