Early Treatment of NOD Mice With B7-H4 Reduces the Incidence of Autoimmune Diabetes

Abstract

OBJECTIVEAutoimmune diabetes is a T cell–mediated disease in which insulin-producing β-cells are destroyed. Autoreactive T cells play a central role in mediating β-cell destruction. B7-H4 is a negative cosignaling molecule that downregulates T-cell responses. In this study, we aim to determine the role of B7-H4 on regulation of β-cell–specific autoimmune responses.RESEARCH DESIGN AND METHODSPrediabetic (aged 3 weeks) female NOD mice (group 1, n = 21) were treated with intraperitoneal injections of B7-H4.Ig at 7.5 mg/kg, with the same amount of mouse IgG (group 2, n = 24), or with no protein injections (group 3, n = 24), every 3 days for 12 weeks.RESULTSB7-H4.Ig reduced the incidence of autoimmune diabetes, compared with the control groups (diabetic mice 28.6% of group 1, 66.7% of group 2 [P = 0.0081], and 70.8% of group 3 [group 1 vs. 3, P = 0.0035]). Histological analysis revealed that B7-H4 treatment did not block islet infiltration but rather suppressed further infiltrates after 9 weeks of treatment (group 1 vs. 2, P = 0.0003). B7-H4 treatment also reduced T-cell proliferation in response to GAD65 stimulation ex vivo. The reduction of diabetes is not due to inhibition of activated T cells in the periphery but rather to a transient increase of Foxp3+ CD4+ T-cell population at one week posttreatment (12.88 ± 1.29 vs. 11.58 ± 1.46%; n = 8; P = 0.03).CONCLUSIONSOur data demonstrate the protective role of B7-H4 in the development of autoimmune diabetes, suggesting a potential means of preventing type 1 diabetes by targeting the B7-H4 pathway.

B7-H4 as a protective shield for pancreatic islet beta cells

“…Both intraperitoneal injections of B7-H4 Ig and cell-associated B7-H4 inhibited proliferation and cytotoxicity of CD4 + and CD8 + T cells in vitro [22][23][24]32] . Juvenile NOD mice treated with B7-H4 Ig exhibited significantly later onset as well as reduced incidence of diabetes [31] . This coincided with a reduction in proliferation and activation of both CD4 + and CD8 + subsets of T cells in the islet infiltrates [31] .…”

“…Juvenile NOD mice treated with B7-H4 Ig exhibited significantly later onset as well as reduced incidence of diabetes [31] . This coincided with a reduction in proliferation and activation of both CD4 + and CD8 + subsets of T cells in the islet infiltrates [31] . In support of this, our preliminary findings suggested that β-cell specific over-expression of B7-H4 in transgenic NOD mice significantly decreased T1D incidence compared with wild type NOD mice (unpublished data).…”

“…Genome-wide association studies have also uncovered certain Single Nucleotide Polymorphisms within the B7-H4-encoding VTCN1 gene as disease-causing in the context of diabetes, further implicating B7-H4 as a potential regulator of T1D [29] . Immunosuppressive functions of B7-H4 was confirmed in experimental T1D models using B7-H4-immunoglobulin (B7-H4 Ig), a recombinant protein derived from fusion of the immunoglobulin constant region to the extracellular domain of B7-H4 [30,31] . Both intraperitoneal injections of B7-H4 Ig and cell-associated B7-H4 inhibited proliferation and cytotoxicity of CD4 + and CD8 + T cells in vitro [22][23][24]32] .…”

“…Conversely, adoptive transfer of diabetogenic T cells into B7-H4 deficient mice resulted in more exacerbated disease than wild-type controls [27] . It was hypothesized that B7-H4 did not have an effect on recruitment of immune infiltrates during the pre-diabetic stage, but rather, it prevented the progression of insulitis to overt diabetes by arresting severe insulitis at 12 wk of age in NOD mice [27,31] . This modulation of immune status at later stage of disease may be associated with down-regulation of the Th1 cells, which are widely accepted as key mediators of autoimmune diseases [31] .…”

“…It was hypothesized that B7-H4 did not have an effect on recruitment of immune infiltrates during the pre-diabetic stage, but rather, it prevented the progression of insulitis to overt diabetes by arresting severe insulitis at 12 wk of age in NOD mice [27,31] . This modulation of immune status at later stage of disease may be associated with down-regulation of the Th1 cells, which are widely accepted as key mediators of autoimmune diseases [31] . Mechanistic studies examining the role of B7-H4 showed that it was able to limit autoreactive CTLs, and suppressed secretion of inflammatory cytokines in the periphery [33] .…”