Identification of a Novel OX40L+ Dendritic Cell Subset That Selectively Expands Regulatory T-Cells

Granulocyte macrophage-colony stimulating factor (GM-CSF) has been demonstrated to play a protective role in autoimmune disease through the dendritic cell-mediated expansion of regulatory T-cells (Tregs). We have previously shown that GM-CSF derived bone-marrow dendritic cells (G-BMDCs) can induce expansion of Tregs through the surface-bound molecule OX40L; however, the physiological relevance of this ex vivo derived DC subset remained to be elucidated. We determined OX40L+G-BMDCs, and not OX40L-G-BMDCs, were responsible for the selective expansion of Tregs expressing functionally suppressive markers. Phenotypic characterization of OX40L+G-BMDCs revealed higher expression levels of co-stimulatory/co-inhibitory molecules, CD80, CD86, and PDL2. Furthermore, OX40L+CD11c+ cells, phenotypically and functionally similar to OX40L+G-BMDCs, were identified in the spleen, brachial lymph nodes and liver of GM-CSF treated mice, but absent in the thymus. Concordantly, the percentage of functionally suppressive Tregs was increased in the spleen, brachial lymph nodes, and liver, of GM-CSF treated mice, but not the thymus, implying a role for OX40L+ DCs in peripheral Treg expansion. Microarray analysis of OX40L+G-BMDCs and OX40L-G-BMDCs revealed significant differences in the expression of PDL2, IL33, CCL17, and CCL22 molecules which could play important roles in the tolerogenic function of OX40L+CD11c+ DCs. Comparing the transcriptome data from OX40L+ G-BMDCs to that of all immune cell types from the ImmGen database revealed OX40L+ G-BMDCs to be distinct from steady-state immune cells. These findings suggest that OX40L+CD11c+ DCs represent a unique tolerogenic DC subset which may play an essential role in maintaining Treg homeostasis and suppressing autoimmunity

Age-dependent divergent effects of OX40L treatment on the development of diabetes in NOD mice

<p>Earlier, we have shown that GM-CSF derived bone marrow (BM) dendritic cells (G-BMDCs) can expand Foxp3⁺ regulatory T-cells (Tregs) through a TCR-independent, but IL-2 dependent mechanism that required OX40L/OX40 interaction. While some reports have shown suppression of autoimmunity upon treatment with an OX40 agonist, others have shown exacerbation of autoimmune disease instead. To better understand the basis for these differing outcomes, we compared the effects of OX40L treatment in 6-week-old pre-diabetic and 12-week-old near diabetic NOD mice. Upon treatment with OX40L, 6-week-old NOD mice remained normoglycemic and showed a significant increase in Tregs in their spleen and lymph nodes, while 12-week-old NOD mice very rapidly developed hyperglycemia and failed to show Treg increase in spleen or LN. Interestingly, OX40L treatment increased Tregs in the thymus of both age groups. However, it induced Foxp3⁺CD103⁺CD38⁻ stable-phenotype Tregs in the thymus and reduced the frequency of autoreactive Teff cells in 6-week-old mice; while it induced Foxp3⁺CD103⁻CD38⁺ labile-phenotype Tregs in the thymus and increased autoreactive CD4⁺ T cells in the periphery of 12-week-old mice. This increase in autoreactive CD4⁺ T cells was likely due to either a poor suppressive function or conversion of labile Tregs into Teff cells. Using <i>ex vivo</i> cultures, we found that the reduction in Treg numbers in 12-week-old mice was likely due to IL-2 deficit, and their numbers could be increased upon addition of exogenous IL-2. The observed divergent effects of OX40L treatment were likely due to differences in the ability of 6- and 12-week-old NOD mice to produce IL-2.</p

An <em>ACACB</em> Variant Implicated in Diabetic Nephropathy Associates with Body Mass Index and Gene Expression in Obese Subjects

<div><p>Acetyl coenzyme A carboxylase B gene (<i>ACACB</i>) single nucleotide polymorphism (SNP) rs2268388 is reproducibly associated with type 2 diabetes (T2DM)-associated nephropathy (DN). <i>ACACB</i> knock-out mice are also protected from obesity. This study assessed relationships between rs2268388, body mass index (BMI) and gene expression in multiple populations, with and without T2DM. Among subjects without T2DM, rs2268388 DN risk allele (T) associated with higher BMI in Pima Indian children (n = 2021; p-additive = 0.029) and African Americans (AAs) (n = 177; p-additive = 0.05), with a trend in European Americans (EAs) (n = 512; p-additive = 0.09), but not Germans (n = 858; p-additive = 0.765). Association with BMI was seen in a meta-analysis including all non-T2DM subjects (n = 3568; p-additive = 0.02). Among subjects with T2DM, rs2268388 was not associated with BMI in Japanese (n = 2912) or EAs (n = 1149); however, the T allele associated with higher BMI in the subset with BMI≥30 kg/m² (n = 568 EAs; p-additive = 0.049, n = 196 Japanese; p-additive = 0.049). Association with BMI was strengthened in a T2DM meta-analysis that included an additional 756 AAs (p-additive = 0.080) and 48 Hong Kong Chinese (p-additive = 0.81) with BMI≥30 kg/m² (n = 1575; p-additive = 0.0033). The effect of rs2268388 on gene expression revealed that the T risk allele associated with higher <i>ACACB</i> messenger levels in adipose tissue (41 EAs and 20 AAs with BMI>30 kg/m²; p-additive = 0.018) and ACACB protein levels in the liver tissue (mixed model p-additive = 0.03, in 25 EA bariatric surgery patients with BMI>30 kg/m² for 75 exams). The T allele also associated with higher hepatic triglyceride levels. These data support a role for <i>ACACB</i> in obesity and potential roles for altered lipid metabolism in susceptibility to DN.</p> </div

Association of rs2268388(C/T) with BMI in full-heritage Pima Indian longitudinal cohort.

<p>model 1: > = 1 nondiabetic exam age <18 and subsequently developed DM; total n = 642; total exam N = 5321;</p><p>P values were adjusted for age, gender, sibship, and repeated exams (matrix: autoregressive; additive genetic model).</p><p>model 2: All individuals- all examinations; total n = 3197; total exam N = 19385;</p><p>P values were adjusted for age, gender, sibship, diabetic status, duration of diabetes, and repeated exams (matrix: autoregressive; additive genetic model).</p><p>T allele is defined as risk allele for higher BMI z-score.</p><p>n_CC, n_CT, n_TT: number of individuals in each genotypic group. N_exams: number of exams.</p

Liver ACACB expression by rs2268388.

<p>Liver ACACB expression by rs2268388.</p

Association of rs2268388 with BMI in non-diabetic subjects.

<p>Association of rs2268388 with BMI in non-diabetic subjects.</p

Liver cell triglyceride (TG) by rs2268388.

<p>Liver cell triglyceride (TG) by rs2268388.</p

Demographic data of the study cohorts.

<p>EA: European American; AA: African American.</p>*<p>The analysis used age & sex standardized z scores (mean: 0.288±1.04). Mean shown is mean of max z-scores converted to BMI units using mean & SD of 12 year-old females.</p>**<p>Age shown is age at max BMI z-score; not necessarily same as age at max BMI.</p>***<p>max BMI from age >15 yrs. N = 637 since 5 kids had no exams after age 15.</p