Autoantibodies reactive to PEP08 are clinically related with morbidity and severity of interstitial lung disease in connective tissue diseases

A Interacting Model: How TRIM21 Orchestrates with Proteins in Intracellular Immunity

Tripartite motif-containing protein 21 (TRIM21), identified as both a cytosolic E3 ubiquitin ligase and FcR (Fragment crystallizable receptor), primarily interacts with proteins via its PRY/SPRY domains and promotes their proteasomal degradation to regulate intracellular immunity. But how TRIM21 involves in intracellular immunity still lacks systematical understanding. Herein, it is probed into the TRIM21-related literature and raises an interacting model about how TRIM21 orchestrates proteins in cytosol. In this novel model, TRIM21 generally interacts with miscellaneous protein in intracellular immunity in two ways: For one, TRIM21 solely plays as an E3, ubiquitylating a glut of proteins that contain specific interferon-regulatory factor, nuclear transcription factor kappaB, virus sensors and others, and involving inflammatory responses. For another, TRIM21 serves as both E3 and specific FcR that detects antibody-complexes and facilitates antibody destroying target proteins. Correspondingly delineated as Fc-independent signaling and Fc-dependent signaling in this review, how TRIM21's interactions contribute to intracellular immunity, expecting to provide a systematical understanding of this important protein and invest enlightenment for further research on the pathogenesis of related diseases and its prospective application is elaborated.

Clinical features and prognostic factors of anti-melanoma differentiation-associated gene 5 antibody-positive dermatomyositis with rapidly progressive interstitial lung disease in Chinese patients

OBJECTIVE

The objective of this study is to investigate clinical features and prognostic factors of antimelanoma differentiation-associated gene 5 (anti-MDA5)-positive dermatomyositis with rapidly progressive interstitial lung disease (RP-ILD) in Chinese patients.

METHODS

Clinical features and prognostic factors of patients with newly diagnosed or recurrent dermatomyositis patients were retrospectively analyzed. All patients were divided into the anti-MDA5-positive or negative dermatomyositis, and with or without RP-ILD groups. Clinical features and prognostic factors were statistically compared among different groups.

RESULTS

The serum ferritin (SF) levels (1500.0 [658.80, 1844.0]) and γ-glutamyl transpeptidase (γ-GT) (125.5 [61.0, 232.0] vs. 28 [16.0, 41.0], Z = 5.528; p < .001) were markedly higher, and phosphocreatine myoenzyme (CK) (73.0 [42.0, 201.0] vs. 1333.0 [79.0, 8000.0], Z = -2.739, p = .006), serum albumin level (32.51 ± 5.23 vs. 35.81 ± 5.88, t = -2.542, p = .013), and lymphocyte count (0.80 ± 0.36 vs. 1.45 ± 0.77, t = -4.717, p < .001) were lower than those in anti-MDA5-negative counterparts. Among patients with anti-MDA5 antibody (Ab) with RP-ILD, the SF level (1531.0 [1163.8, 2016.5] vs. 584.9 [564.8, 1042.5], Z = 2.664, p = .008), γ-GT (134.0 [81.0, 204.5] vs. 123.0 [76.0, 189.0], Z = 3.136, p = .002) and positive rate of anti-RO-52 Ab (90.9% vs. 50.0%, χ2  = 7.222, p = .013) were higher and lymphocyte count (0.79 ± 0.38 vs. 1.32 ± 0.74, t = -3.025, p = .029) was lower than those in their counterparts without RP-ILD. The SF level of anti-MDA5 nonsurvivors (1544 [1447.32, 2089.0] vs. 584.9 [515.7, 1500.0], Z = 2.096, p = .030), anti-RO-52 Ab-positive rate ([16/18, 88.9%] vs. [9/16, 56.2%], χ2  = 4.636, p = .031) were higher than those in survivors. Lymphocytopenia was a risk factor for RP-ILD and death of patients with anti-MDA5-positive dermatomyositis. The area under receiver operating characteristic curve was 0.888 (95% confidence interval: 0.756, 1.000; p < .001), the sensitivity was 85.7%, the specificity was 93.8%, and Youden's index was 0.795.

CONCLUSIONS

Anti-MDA5-positive dermatomyositis patients are prone to developing RP-ILD. Declined lymphocyte count is a critical risk factor for RP-ILD, probably acting as a simple and effective predictor for Chinese patients with anti-MDA5-positive dermatomyositis.

Cloning of human anti-factor XIII monoclonal antibody dissects mechanisms of polyclonal antibodies in a single patient

BACKGROUND

Coagulation factor XIII (FXIII) consists of 2 A (FXIII-A) and 2 B (FXIII-B) subunits that cross-link and strengthen the hemostatic fibrin thrombus; thus, abnormal bleeding occurs when FXIII is significantly reduced. Autoimmune-acquired FXIII deficiency (AiF13D) is characterized by lethal bleeding secondary to the development of autoantibodies against FXIII. However, since anti-FXIII autoantibodies are polyclonal, the mechanism underlying FXIII dysfunction is unclear.

OBJECTIVES

The objective of this study was to dissect the inhibitory mechanisms of polyclonal anti-FXIII autoantibodies.

METHODS

In this study, we prepared the human monoclonal antibodies (hmAbs) from the peripheral blood of an 86-year-old man with AiF13D by using a new complementary DNA cloning method and analyzed the properties of each autoantibody.

RESULTS

Seventeen clones obtained from hmAbs were divided into the following 3 groups: dissociation inhibitors of FXIII-A₂B₂ (6 clones), assembly inhibitors of FXIII-A₂B₂ (3 clones), and nonneutralizing/inhibitory hmAbs (8 clones). Dissociation inhibitors strongly inhibited fibrin cross-linking and amine incorporation. Assembly inhibitors extracted FXIII-A from FXIII-A₂B₂, strongly inhibited binding of FXIII-A to FXIII-B, and activation peptide cleavage. However, the patient's plasma presented a strong inhibition of A₂B₂ heterodimer assembly but only a slight inhibition of thrombin-Ca²⁺-dependent dissociation, suggesting that the assembly inhibitors concealed the effect of dissociation inhibitors in plasma. By contrast, nonneutralizing antibodies had little effect on the function of FXIII, suggesting that nonneutralizing hmAbs (and/or dissociation inhibitors and/or assembly inhibitors) promoted the clearance of FXIII-A from the blood.

CONCLUSION

Cloning of anti-FXIII autoantibodies enabled us to not only elucidate the mechanism and pathophysiology of AiF13D but also develop a completely new type of anticoagulant.

Clinical significance of myositis-specific autoantibody profiles in Japanese patients with polymyositis/dermatomyositis

Myositis-specific autoantibodies, such as anti-melanoma differentiation associated gene 5 (MDA5) and anti-anti-amino acyl-tRNA synthetases (ARS) antibodies, are associated with interstitial lung diseases (ILD), which determine the prognosis of polymyositis/dermatomyositis (PM/DM) patients. However, there is a paucity of data on the clinical correlation between anti-Sjögren syndrome-related antigen A (anti-SSA)/Ro52 antibodies in PM/DM. We investigated the prevalence of myositis-specific autoantibodies including anti-SSA/Ro52 antibody and assessed the clinical significance of these antibodies in patients with PM/DM.We retrospectively reviewed demographic data and clinical outcomes in patients with PM/DM. The study population comprised 24 patients with PM and 60 patients with DM. The presence of anti-myositis-specific antibodies (MDA5, ARS, Jo-1, SSA/Ro52) was determined by immunosorbent assay (ELISA).Anti-MDA5 antibody was detected in 18 patients with DM (n = 60). Anti-ARS/anti-SSA/Ro52 antibodies were detected in 31 and 39 patients with PM/DM (n = 84). Rapidly progressive ILD patients were mainly found in the anti-MDA5 antibody-positive DM group. During the follow-up period, 9 patients died. Kaplan-Meier analysis demonstrated that survival rates seem to be lower in DM patients with anti-MDA5 antibodies compared with those without anti-MDA5 antibodies. Furthermore, dual positivity for anti-SSA/Ro52 and anti-MDA5 antibodies was significantly higher in nonsurviving DM patients compared with survivors.Although the presence of anti-ARS or anti-MDA5 antibodies is a prognostic marker in patients with PM/DM, combined presence of anti-SSA/Ro52 and anti-MDA5 antibodies represent another marker for clinical outcome in DM patients. Our results suggest that anti-SSA/Ro52 antibody positivity in DM patients with anti-MDA5 antibody reveals a subgroup of DM patients with poor prognosis.