Prevention of autoimmune diabetes by ectopic pancreatic ß-cell expression of interleukin-35.

Interleukin (IL)-35 is a newly identified inhibitory cytokine used by T regulatory cells to control T cell-driven immune responses. However, the therapeutic potential of native, biologically active IL-35 has not been fully examined. Expression of the heterodimeric IL-35 cytokine was targeted to ß-cells via the rat insulin promoter (RIP) II. Autoimmune diabetes, insulitis, and the infiltrating cellular populations were analyzed. Ectopic expression of IL-35 by pancreatic ß-cells led to substantial, long-term protection against autoimmune diabetes, despite limited intraislet IL-35 secretion. Nonobese diabetic RIP-IL35 transgenic mice exhibited decreased islet infiltration with substantial reductions in the number of CD4(+) and CD8(+) T cells, and frequency of glucose-6-phosphatase catalytic subunit-related protein-specific CD8(+) T cells. Although there were limited alterations in cytokine expression, the reduced T-cell numbers observed coincided with diminished T-cell proliferation and G1 arrest, hallmarks of IL-35 biological activity. These data present a proof of principle that IL-35 could be used as a potent inhibitor of autoimmune diabetes and implicate its potential therapeutic utility in the treatment of type 1 diabetes.

T cell islet accumulation in type 1 diabetes is a tightly regulated, cell-autonomous event.

Type 1 diabetes is a T cell-mediated autoimmune disease, characterized by lymphocytic infiltration of the pancreatic islets. It is currently thought that islet antigen specificity is not a requirement for islet entry and that diabetogenic T cells can recruit a heterogeneous bystander T cell population. We tested this assumption directly by generating T cell receptor (TCR) retrogenic mice expressing two different T cell populations. By combining diabetogenic and nondiabetogenic or nonautoantigen-specific T cells, we demonstrate that bystander T cells cannot accumulate in the pancreatic islets. Autoantigen-specific T cells that accumulate in islets, but do not cause diabetes, were also unaffected by the presence of diabetogenic T cells. Additionally, 67% of TCRs cloned from nonobese diabetic (NOD) islet-infiltrating CD4(+) T cells were able to mediate cell-autonomous islet infiltration and/or diabetes when expressed in retrogenic mice. Therefore, islet entry and accumulation appears to be a cell-autonomous and tightly regulated event and is governed by islet antigen specificity.

On the pathogenicity of autoantigen-specific T-cell receptors.

OBJECTIVE: Type 1 diabetes is mediated by T-cell entry into pancreatic islets and destruction of insulin-producing beta-cells. The relative contribution of T-cells specific for different autoantigens is largely unknown because relatively few have been assessed in vivo. RESEARCH DESIGN AND METHODS: We generated mice possessing a monoclonal population of T-cells expressing 1 of 17 T-cell receptors (TCR) specific for either known autoantigens (GAD65, insulinoma-associated protein 2 (IA2), IA2beta/phogrin, and insulin), unknown islet antigens, or control antigens on a NOD.scid background using retroviral-mediated stem cell gene transfer and 2A-linked multicistronic retroviral vectors (referred to herein as retrogenic [Rg] mice). The TCR Rg approach provides a mechanism by which T-cells with broad phenotypic differences can be directly compared. RESULTS: Neither GAD- nor IA2-specific TCRs mediated T-cell islet infiltration or diabetes even though T-cells developed in these Rg mice and responded to their cognate epitope. IA2beta/phogrin and insulin-specific Rg T-cells produced variable levels of insulitis, with one TCR producing delayed diabetes. Three TCRs specific for unknown islet antigens produced a hierarchy of insulitogenic and diabetogenic potential (BDC-2.5 > NY4.1 > BDC-6.9), while a fourth (BDC-10.1) mediated dramatically accelerated disease, with all mice diabetic by day 33, well before full T-cell reconstitution (days 42-56). Remarkably, as few as 1,000 BDC-10.1 Rg T-cells caused rapid diabetes following adoptive transfer into NOD.scid mice. CONCLUSIONS; Our data show that relatively few autoantigen-specific TCRs can mediate islet infiltration and beta-cell destruction on their own and that autoreactivity does not necessarily imply pathogenicity.

Human IL-19 regulates immunity through auto-induction of IL-19 and production of IL-10.

IL-19 is a novel, recently identified member of the IL-10 family of cytokines. We identified IL-10 as a cytokine that was strongly induced in IL-19-stimulated PBMC. IL-19-induced IL-10 secretion was dose-dependent and could be detected in culture supernatants after 3 h of stimulation. Furthermore, quantitative RT-PCR analysis demonstrated that IL-19 stimulation increased the level of IL-10 mRNA present within cells, suggesting that IL-19 is a transcriptional activator of IL-10. IL-19 was also able to induce its own expression, with IL-10 potently down-regulating this IL-19 'auto-induction'. LPS induction of IL-19 expression was also regulated by IL-10, demonstrating that IL-10 is likely an important regulator of human IL-19 induction. Maturation of dendritic cells from human PBMC in the presence of IL-19 resulted in an increase in IL-10 levels within these cells, whereas IL-12 was not affected. These results advance our understanding of the function of this novel cytokine and its regulation within the human immune system, in addition to providing a new insight into the control of the important immunoregulatory cytokine, IL-10.

Human interleukin-19 and its receptor: a potential role in the induction of Th2 responses.

Interleukin-19 (IL-19) is a newly discovered member of the IL-10 family of ligands whose function is presently undefined. We recently described its cloning and initial characterization and in so doing, noted that the induction of IL-19 by LPS in human monocytes was down-regulated by interferon-gamma (IFN-gamma) and up-regulated by IL-4. This preliminary observation led us to speculate that IL-19 may play a role in the Th1/Th2 system and we examined this hypothesis further. Our results suggested that IL-19 is able to influence the maturation of human T-cells. CD4+ T-cells resulting from SEB stimulation in the presence of IL-19 contained a higher proportion of IL-4 producing cells than those developing in the absence of IL-19. This observation was complimented by the observation that fewer IFN-gamma cells accrued in the presence of IL-19, thereby suggesting that IL-19 altered the balance of Th1/Th2 cells in favour of Th2. Furthermore, in whole PBMC cultures, IL-19 up-regulated IL-4 and down-regulated IFNgamma in a dose-dependent manner. These results are presented here in review format, in the context of an overall discussion of IL-19 and its receptor.

Natural killer cell receptor expression by human first trimester decidual granular leukocytes and T-lymphocytes.

PROBLEM: Detailed analysis of the expression of natural killer (NK) cell activatory and inhibitory receptors by human decidual leukocyte subpopulations has not been undertaken. METHOD OF STUDY: Expression of the natural cytotoxicity receptors NKp30, NKp44 and NKp46 by decidual leukocytes were studied by reverse transcriptase polymerase chain reaction. Expression of the killer cell Ig-like receptors CD158a and CD158b on decidual T cells were studied by flow cytometry. RESULTS: First trimester decidual leukocytes expressed mRNA for the NKp30 and NKp46 receptors but expression of NKp44, a marker of activated NK cells, was not detected. A mean of 11.8 and 15.8% of decidual T cells expressed CD158a or 158b, respectively, while only around 1% of peripheral blood T cells were CD158a+ or CD158b+. CONCLUSIONS: Like peripheral blood NK cells, decidual NK cells express the natural cytotoxicity receptors NKp30 and NKp46 but the significance of this will not become apparent until ligands for these molecules have been identified. Only a minority of decidual T cells express CD158, indicating that this is not a mechanism for inhibition of cytotoxicity mediated by all decidual T cells.