Polyreactive antigen-binding B cells in the peripheral circulation are IgD+ and B7−

Polyreactive antibodies are naturally occurring antibodies, primarily of the IgM isotype, that are capable of reacting with a wide variety of different self and non-self antigens. Previously, we reported that a B cell capable of making polyreactive antibody has Ig receptors on its surface that can bind different antigens. The present investigation was initiated to characterize these polyreactive antigen-binding B cells further. A panel of fluorescein isothiocyanate-labeled antigens (insulin, IgG Fc fragment or β-galactosidase) served as probes to select polyreactive antigen-binding B cells by cell sorting. Our experiment revealed that these polyreactive antigen-binding B cells were mainly of the IgD isotype. They expressed high levels of CD40 and major histocompatibility complex class II molecules, but little or no B7-1, B7-2, or Fas. In contrast to the binding of antigens to monoreactive receptors (usually high affinity), the binding of antigens to polyreactive receptors (usually moderate or low affinity) did not up-regulate the expression of B7-1 or B7-2. Antigens that bound to polyreactive receptors, however, were internalized and degraded, although not as efficiently as antigens that bound to monoreactive receptors. Despite the ability of these B7⁻ cells to process antigens, they were not able to activate T cells in a mixed leukocyte reaction. It is concluded that polyreactive antigen-binding B cells have properties that are consistent with the ability to induce immunological tolerance.     

Targeted disruption of the protein tyrosine phosphatase-like molecule IA-2 results in alterations in glucose tolerance tests and insulin secretion

IA-2 is a major autoantigen in type 1 diabetes. Autoantibodies to IA-2 appear years before the development of clinical disease and are being widely used as predictive markers to identify individuals at risk for developing type 1 diabetes. IA-2 is an enzymatically inactive member of the transmembrane protein tyrosine phosphatase family and is an integral component of secretory granules in neuroendocrine cells. To study its function, we generated IA-2-deficient mice. Northern and Western blot analysis showed that neither IA-2 mRNA nor protein was expressed. Physical examination of the IA-2(- /-) animals and histological examination of tissues failed to reveal any abnormalities. Nonfasting blood glucose levels, measured over 6 months, were slightly elevated in male IA-2(-/-) as compared to IA-2(+ /+) littermates, but remained within the nondiabetic range. Glucose tolerance tests, however, revealed statistically significant elevation of glucose in both male and female IA-2(-/-) mice and depressed insulin release. In vitro glucose stimulation of isolated islets showed that male and female mice carrying the disrupted gene released 48% (P < 0.001) and 42% (P < 0.01) less insulin, respectively, than mice carrying the wild-type gene. We concluded that IA-2 is involved in glucose-stimulated insulin secretion.     

病毒序列促转基因在斑马鱼胚胎发育过程中的高效表达

目的探讨转基因在斑马鱼胚胎发育过程中高效表达的有效途径和手段。方法以增强处理的绿色荧光蛋白(GFP)作为报告基因,在表达质粒的两翼连接构建腺关联病毒(adeno-assoc iated virus,AAV)来源的病毒性反转末端重复序列(inverted term inal repeats,ITR s),以显微注射方式注入斑马鱼受精卵的单一细胞和双细胞时相。结果病毒序列中的ITR s可使转基因表达效率达到33.0%,远远高于未与病毒序列结合的质粒。结论源于病毒的ITR s可显著促进转基因在斑马鱼胚胎发育过程中的表达。     

Dense core vesicle proteins IA-2 and IA-2beta: metabolic alterations in double knockout mice

IA-2 and IA-2beta are members of the transmembrane protein tyrosine phosphatase family located in dense core vesicles of neuroendocrine cells, including the beta-cells of pancreatic islets. In the present study, by mating C57BL/6Nci IA-2(+/-) with IA-2beta(+/-) mice, we generated double knockout mice (IA-2(-/-)/IA-2beta(-/-)) to study the effect of the combined deletion of these two proteins on insulin secretion and blood glucose levels. The double knockout mice appeared healthy at birth and showed normal growth and development. Histological examination and immunostaining for insulin, glucagon, somatostatin, and pancreatic polypeptide revealed no difference between the double knockout and wild-type mice. Nonfasting blood glucose and insulin levels also were within the normal range. However, compared with the wild-type mice, the double knockout mice showed glucose intolerance and an absent first-phase insulin release curve. No evidence of insulin resistance was observed nor were there alterations in fasting blood glucose, insulin, or leptin levels in the double knockout mice maintained on a high-fat diet compared with the wild-type mice maintained on the same diet. In addition, to determine whether the combined deletion of IA-2 and IA-2beta played any role in the development of diabetes in NOD mice, we generated double knockout mice on the NOD/LtJ background. The incidence of diabetes in these mice was not significantly different than that in the wild-type mice. Taken together, our experiments show that the dense core vesicle proteins IA-2 and IA-2beta, alone or in combination, are involved in insulin secretion, but neither alone nor in combination are they required for the development of diabetes in NOD mice.     

PREVENTION OF CELL-TO-CELL SPREAD OF HERPES SIMPLEX VIRUS BY LEUKOCYTES

Antibody to herpes simplex virus (HSV) plus complement destroyed HSV-infected cells but did not stop the spread of the infection. Studies on the relationship between the time of appearance of viral antigens on the cell surface, immunological destruction of the cells by antiviral antibody and complement, and transfer of the virus to adjacent cells showed that the virus spread from infected to uninfected cells before the infected cells were susceptible to immunological destruction. Incubation of infected monolayers with leukocytes, however, stopped the spread of the virus by nonspecifically damaging both infected and uninfected cells and by presumably breaking intercellular bridges. When leukocytes were removed from infected monolayers, viral plaques developed. If, however, antiviral antibody and complement were added to monolayers before the leukocytes were removed, the development of plaques was prevented. These findings suggest that both antibody and leukocytes are needed to cure HSV infections.     

Targeted disruption of the IA-2beta gene causes glucose intolerance and impairs insulin secretion but does not prevent the development of diabetes in NOD mice

Insulinoma-associated protein (IA)-2beta, also known as phogrin, is an enzymatically inactive member of the transmembrane protein tyrosine phosphatase family and is located in dense-core secretory vesicles. In patients with type 1 diabetes, autoantibodies to IA-2beta appear years before the development of clinical disease. The genomic structure and function of IA-2beta, however, is not known. In the present study, we determined the genomic structure of IA-2beta and found that both human and mouse IA-2beta consist of 23 exons and span approximately 1,000 and 800 kb, respectively. With this information, we prepared a targeting construct and inactivated the mouse IA-2beta gene as demonstrated by lack of IA-2beta mRNA and protein expression. The IA-2beta(-/-) mice, in contrast to wild-type controls, showed mild glucose intolerance and impaired glucose-stimulated insulin secretion. Knockout of the IA-2beta gene in NOD mice, the most widely studied animal model for human type 1 diabetes, failed to prevent the development of cyclophosphamide-induced diabetes. We conclude that IA-2beta is involved in insulin secretion, but despite its importance as a major autoantigen in human type 1 diabetes, it is not required for the development of diabetes in NOD mice.     

Melanoma differentiation-associated gene 7/interleukin (IL)-24 is a novel ligand that regulates angiogenesis via the IL-22 receptor

The melanoma differentiation-associated gene 7 (mda-7), also called interleukin (IL)-24, suppresses the growth of some cancers in vitro and in vivo as a result of the ectopic expression of its protein. However, the function of the secreted form of the protein in cancer has not been previously studied. The purpose of this study was to determine the antiangiogenic function of a secreted form of the MDA-7/IL-24 protein (sMDA-7/IL-24). In vitro, sMDA-7/IL-24 inhibited both endothelial cell differentiation and migration of endothelial cells induced by vascular endothelial growth factor and basic fibroblast growth factor. The sMDA-7/IL-24-mediated inhibitory effect was 10-50 times more potent than endostatin, IFN-gamma, and IFN-inducible protein 10 in vitro. Furthermore, the inhibitory effect was not mediated by IFN or IFN-inducible protein 10. IL-22 receptor mediated the antiangiogenic activity of sMDA-7/IL-24. Administration of a blocking antibody to IL-22 receptor in conjunction with sMDA-7/IL-24 led to abrogation of inhibition of endothelial differentiation. sMDA-7/IL-24 inhibited vascular endothelial growth factor-induced angiogenesis as evidenced by reduced vascularization and hemoglobin content in in vivo Matrigel plug assays. In vivo, the growth of human lung tumor cells was significantly inhibited, and vascularization was reduced when the cells were mixed with 293 cells stably expressing sMDA-7/IL-24. Systemic administration of sMDA-7/IL-24 inhibited lung tumor growth in a mouse xenograft model. Associated with tumor growth inhibition was decreased tumor microvessel density and hemoglobin content, indicating the presence of antiangiogenic activity. These data demonstrate that sMDA-7/IL-24 is a novel and potent antiangiogenic effector and support the development of MDA-7/IL-24-based therapeutics.