SUMMARY Mechanisms by which interferon (IFN)-γ activates genes to promote macrophage activation are well studied, but little is known about mechanisms and functions of IFN-γ-mediated gene repression. We used an integrated transcriptomic and epigenomic approach to analyze chromatin accessibility, histone modifications, transcription factor binding, and gene expression in IFN-γ-primed human macrophages. IFN-γ suppressed basal expression of genes corresponding to an ‘M2’-like homeostatic and reparative phenotype. IFN-γ repressed genes by suppressing the function of enhancers enriched for binding by transcription factor MAF. Mechanistically, IFN-γ disassembled a subset of enhancers by inducing coordinate suppression of binding by MAF, lineage-determining transcription factors, and chromatin accessibility. Genes associated with MAF-binding enhancers were suppressed in macrophages isolated from rheumatoid arthritis patients, revealing a disease-associated signature of IFN-γ–mediated repression. These results identify enhancer inactivation and disassembly as a mechanism of IFN-γ-mediated gene repression, and reveal MAF as a regulator of the macrophage enhancer landscape that is suppressed by IFN-γ to augment macrophage activation.

Dysregulated IL-23/IL-17 responses have been linked to psoriatic arthritis and other forms of spondyloarthritides (SpA). RORγt, the key Thelper17 (Th17) cell transcriptional regulator, is also expressed by subsets of innate-like T cells, including invariant natural killer T (iNKT) and γδ-T cells, but their contribution to SpA is still unclear. Here we describe the presence of particular RORγt+T-betloPLZF− iNKT and γδ-hi T cell subsets in healthy peripheral blood. RORγt+ iNKT and γδ-hi T cells show IL-23 mediated Th17-like immune responses and were clearly enriched within inflamed joints of SpA patients where they act as major IL-17 secretors. SpA derived iNKT and γδ-T cells showed unique and Th17-skewed phenotype and gene expression profiles. Strikingly, RORγt inhibition blocked γδ17 and iNKT17 cell function while selectively sparing IL-22+ subsets. Overall, our findings highlight a unique diversity of human RORγt+ T cells and underscore the potential of RORγt antagonism to modulate aberrant type 17 responses.

SummaryGenetic studies have indicated that susceptibility to rheumatoid arthritis (R.A) maps to the HLA-DP, locus of the major histocompatibility complex. Strong linkage disequilibrium between certain HLA-DQ genes and HLA-DP,. genes associated with RA, however, suggests that HLA-DQ molecules may also play a role in RA susceptibility. To examine the role of HLA-DQ molecules in arthritis, we generated transgenic mice expressing the DQA 1"0301 and DQB 1"0302 genes from an RA predisposing haplotype (DQ8/DR.4Dw4). The transgenes were introduced into mouse class II-deficient H-2Ab ~ mice, and their susceptibility to experimental collagen-induced arthritis was evaluated. The HLA-DQ8+,H-2Ab ~ mice displayed good expression of the DQ8 molecule, while no surface expression of endogenous murine class II molecules could be detected. The DQ8 molecule also induced the selection of CD4 + T cells expressing a normal repertoire of V~ T cell receptors. Immunization of HLA-DQ8+,H-2Ab ~ mice with bovine type II collagen (CII) induced a strong antibody response that was crossreactive to homologous mouse CII. Also, in vitro proliferative responses against bovine CII, which were blocked in the presence of an antibody specific for HLA-DQ and mouse CD4, were detected. Finally, a severe polyarthritis developed in a majority of HLA-DQ8+,H-2Ab ~ mice, which was indistinguishable from the disease observed in arthritis susceptible B10.T(6R) (H-2Aq) controls. In contrast, HLA-DQ8-,H-2Ab ~ fullsibs did not generate CII antibody and were completely resistant to arthritis. Therefore, these results strongly suggest that HLA-DQ8 molecules contribute to genetic susceptibility to arthritis and also estabhsh a novel animal model for the study of human arthritis.I t is widely accepted that a strong genetic component contributes to the susceptibility or resistance to certain human autoimmune diseases (1). Attempts to identify the particular genes involved in these disorders has been an area of major focus for many laboratories, and inroads have been clearly made. Among the numerous genes studied, one group that has garnered much attention are the genes encoding the class I and class II molecules of the HLA complex. Located on the short arm of chromosome 6, the primary function of HLA class I and II molecules is to bind and present processed antigenic peptides to T cells bearing receptors specific for the peptide-HLA complex. This presentation event plays a pivotal role in shaping the cellular immune repertoire and dictating the nature and scope of the immune response against a given antigen (2).A role for HLA molecules in the etiology of autoimmune disease derives from genetic studies showing a clear association between the presence or absence of certain HLA class I or II alleles, as well as increased or decreased susceptibility to a particular autoimmune disorder. A disease with a strong autoimmune foundation and HLA class II association is rheumatoid arthritis (RA) 1. In Caucasians, genetic studies initially showed a high prevalence of the HLA-DR4Dw4...

SummaryMacrophages can fuse to form osteoclasts in bone or multinucleate giant cells (MGCs) as part of the immune response. We use a systems genetics approach in rat macrophages to unravel their genetic determinants of multinucleation and investigate their role in both bone homeostasis and inflammatory disease. We identify a trans-regulated gene network associated with macrophage multinucleation and Kcnn4 as being the most significantly trans-regulated gene in the network and induced at the onset of fusion. Kcnn4 is required for osteoclast and MGC formation in rodents and humans. Genetic deletion of Kcnn4 reduces macrophage multinucleation through modulation of Ca2+ signaling, increases bone mass, and improves clinical outcome in arthritis. Pharmacological blockade of Kcnn4 reduces experimental glomerulonephritis. Our data implicate Kcnn4 in macrophage multinucleation, identifying it as a potential therapeutic target for inhibition of bone resorption and chronic inflammation.

Syntheses and structure-activity relationships (SAR) of nonsteroidal glucocorticoid receptor (GR) agonists are described. These compounds contain azaindole moieties as A-ring mimetics and display various degrees of in vitro dissociation between gene transrepression and transactivation. Collagen induced arthritis studies in mouse have demonstrated that in vitro dissociated compounds (R)-16 and (R)-37 have steroid-like anti-inflammatory properties with improved metabolic side effect profiles, such as a reduced increase in body fat and serum insulin levels, compared to steroids.