Purpose of review: To discuss clinical and pathogenic roles of HLA-B∗51 in Behçet's syndrome. Recent findings: HLA-B∗51 remains the most important genetic factor in Behçet's syndrome, despite the recent identification of several susceptibility genes. The prevalence of HLA-B∗51 has been shown to differ among phenotype-based clinical clusters in the same patient population. HLA-B∗51 shows epistatic interaction with the susceptible allele of endoplasmic reticulum aminopeptidase (ERAP)1 encoding the Hap10 allotype, which has the lowest trimming activity of the MHC-Class I binding peptides. Subsequent molecular studies have suggested that the disease-associated Hap10 allotype is implicated in the generation and selection of the disease protective or promoting peptides loading onto HLA-B∗51, although these pathogenic peptides have yet to be identified. Summary: HLA-B∗51 is a hallmark of Behçet's syndrome but genetic markers are not very useful in the diagnosis of Behçet's syndrome. Rather, it is considered an important factor in determining clinical phenotypes in this heterogeneous condition. The epigenetic interaction of HLA-B∗51 with ERAP1 sheds light on pathogenesis.

Interstitial lung disease (ILD) is the principal cause of death in polymyositis/dermatomyositis (PM/DM). Here we investigated prognostic factors for death and serious infection in PM/DM-ILD using the multicenter database. We retrospectively reviewed baseline demographic, clinical and laboratory findings, treatment regimens and outcomes in patients with PM/DM-ILD. The distribution of ILD lesions was evaluated in four divided lung zones of high-resolution computed tomography images. Of 116 patients with PM/DM-ILD, 14 died within 6 months from the diagnosis. As independent risk factors for early death, extended ILD lesions in upper lung fields (odds ratio (OR) 8.01, p = 0.016) and hypocapnia (OR 6.85, p = 0.038) were identified. Serious infection was found in 38 patients, including 11 patients who died of respiratory or multiple infections. The independent risk factors were high serum KL-6 (OR 3.68, p = 0.027), high initial dose of prednisolone (PSL) (OR 4.18, p = 0.013), and combination immunosuppressive therapies (OR 5.51, p < 0.001). The present study shows the progression of ILD at baseline is the most critical for survival and that infection, especially respiratory infection, is an additive prognostic factor under the potent immunosuppressive treatment.

Innate immunity including macrophages (Mϕ) in lupus nephritis (LN) has been gaining attention, but roles of Mϕ in LN remain uncertain. Immunohistochemical staining was performed to determine CD68, CD163, heme oxygenase (HO)-1 (a stress-inducible heme-degrading enzyme with anti-inflammatory property), pSTAT1, and CMAF-expressing Mϕ in the glomeruli of patients with LN. Effects of type I interferons on the expression levels of CD163, HO-1, BTB and CNC homology 1 (Bach1; a transcriptional HO-1 repressor), interleukin (IL)-6, and IL-10 by human M2-like Mϕ, which were differentiated in vitro from peripheral monocytes with macrophage colony-stimulating factor, were assessed by RT-PCR and immunocytostaining. Clinical manifestations, anti-double-stranded DNA (anti-dsDNA), and local HO-1 expression were compared in Bach1-deficient and wild-type MRL/lpr mice. The number of glomerular M2-like Mϕ correlated with the amounts of proteinuria in patients with LN. Unlike monocyte-derived M2-like Mϕ, HO-1 expression was defective in the majority of glomerular M2-like Mϕ of patients with LN. Stimulation of human M2-like Mϕ with type I interferons led to reduced HO-1 expression and increased Bach1 and IL-6 expression. Bach1-deficient MRL/lpr mice exhibited increased HO-1 expression in kidneys, prolonged survival, reduced urine proteins, and serum blood urea nitrogen levels, but serum anti-dsDNA antibody levels were comparable. Increased expression of CD163 and HO-1 was found in peritoneal Mϕ from Bach1-deficient MRL/lpr mice. Our data suggest that dysregulated M2-like Mϕ play a proinflammatory role in LN. Bach1 is a potential therapeutic target that could restore the anti-inflammatory property of M2 Mϕ.

Low C-C chemokine receptor 1 (CCR1) and interleukin (IL)-10 expression is associated with risk of Behçet’s disease (BD). The objective of the present study was to clarify the pathological roles of CCR1 and IL10 loci identified by previous BD genome-wide association studies (GWASs). M1 and M2 macrophages (Mφ) were differentiated with granulocyte-macrophage colony-stimulating factor or macrophage colony-stimulating factor (M-CSF) from peripheral monocytes of healthy control subjects (HC) and patients with BD. Expression of CD68 and CD163 was evaluated to test for Mφ polarization. CCR1 and IL-10 messenger RNA (mRNA) and protein expression was compared according to CCR1 and IL10 single-nucleotide polymorphism (SNP) genotypes. The migratory ability of M1 and M2 Mφ toward CCR1 ligand macrophage inflammatory protein (MIP)-1α was compared. The ratio of M1 and M2 Mφ in skin lesions of BD and systemic sclerosis (SSc), which was reported to be M2 Mφ-dominant, was compared. To examine the plasticity of polarized Mφ, the differentiated cells were cultured with either the same or the other culture condition. Preferential expression of CD163, CCR1, and IL-10 was found in M2 Mφ compared with M1 Mφ. M2 Mφ migrated more sensitively to low concentrations of MIP-1α than M1 Mφ did. BD-derived M1 Mφ showed higher CCR1 surface expression than HC-derived M1 Mφ did. IL10 and CCR1 mRNA expression differences were observed by GWAS-identified SNP genotypes in polarized Mφ. BD skin lesions showed M1 Mφ predominance compared with SSc skin lesions. A plasticity assay revealed that M-CSF restored IL-10 synthesis and reduced IL-6 production by M1 Mφ. The present study reveals that GWAS-identified SNPs contribute to M1 Mφ-predominant inflammation in BD. Our data also suggest that the skewed Mφ polarization is correctable by immunological intervention.

Background: How HLA-A26 modulates Behçet’s disease ocular lesions such as iridocyclitis and retinochorioiditis has not been scrutinized. Methods: Ministry of Health, Labour and Welfare of Japan provided us a database of Behçet’s disease patients who were registered from 2003 to 2014. We selected patients who satisfied International Criteria for Behçet’s Disease and whose data for HLA-A26 was available. Results. Eligible 557 patients consisting of 238 men (42.7%) and 319 women (57.3%), whose median age was 38 years old (interquartile range (IQR) 29-47) were analyzed. Prevalence of general ocular lesions, iridocyclitis, retinochorioiditis, and chronic lesions were 43.1%, 30.7%, 34.1%, and 17.4%, respectively. The prevalence of ocular lesions was higher among HLA-A26 carriers compared to that among HLA-A26 non-carriers with odds ratio (OR) of 2.5 (95% confidence interval (95% CI) 1.8-3.5, P < 0.001) for general ocular lesions, OR of 2.5 (95% CI 1.7-3.6, P < 0.001) for iridocyclitis, OR of 2.8 (95% CI 1.9-4.0, P < 0.001) for retinochorioiditis, and OR of 2.7 (95% CI 1.7-4.3, P < 0.001) for “chronic ocular lesion following iridocyclitis or retinochorioiditis.” The HLA-A26 had a similar impact on ocular lesions between HLA-B51 positive and negative cases (Breslow-Day test, P > 0.05). However, the HLA-A26 had a larger impact on iridocyclitis for men compared to women (Breslow-Day test, P = 0.040). The male HLA-A26 carriers had higher risk of iridocyclitis with OR of 3.4 (95%CI 2.0-5.9, P <0.001), while the OR for women was 1.5 (95%CI 0.9-2.6, P = 0.146). Conclusion: HLA-A26 carriers had higher risk for iridocyclitis and retinochorioiditis. However, the impact was more prominent for men.

Behçet’s disease is a chronic relapsing inflammatory disorder characterized by oral and genital ulcers, skin lesions, and uveitis. Although the Involvement of the gastrointestinal, large vascular, and central nervous systems is less common, it can be fatal at times. To suppress inflammatory exacerbations and recurrences which can cause irreversible organ damage, treatment should be individualized according to the disease phenotype and severity. Apremilast, an oral phosphodiesterase 4 inhibitor, is used to treat psoriasis. The enzyme specific inhibitor increases intracellular cAMP levels, which modulate multiple signaling pathways in both innate and adaptive immunocompetent cells, leading to attenuation of inflammatory responses through the suppression of the functions of various types of immunocompetent cells including Th1 cells, Th17 cells and M1 macrophages. Current evidence shows that apremilast is effective for oral ulcer, the most common symptom of Behçet’s disease. An oral ulcer is considered to represent the basic immunopathology of Behçet’s disease, because the disease susceptibility genes are shared between Behçet’s disease and recurrent aphthous stomatitis. The favorable effects have been documented in other inflammatory disease with symptoms similar to those of Behçet’s disease. The further studies would shed the light on the potential of apremilast for the treatment of Behçet’s disease.