Diagnosis and management of the antiphospholipid syndrome

Circulating plasmablasts contribute to antiphospholipid antibody production, associated with type I interferon upregulation

Essentials The mechanism of antiphospholipid antibodies (aPL) production remains unclear. We investigated lymphocyte subset, single nucleotide polymorphisms (SNP), and aPL-producing cells. The increase of circulating plasmablasts was associated with type I interferon upregulation. Our novel ex vivo assay revealed circulating plasmablasts as a major source of aPL. SUMMARY: Background/objective Antiphospholipid antibodies (aPL) are pathogenic autoantibodies in antiphospholipid syndrome (APS). This study aimed to clarify the mechanism of aPL production. Methods T cell and B cell subsets were evaluated in peripheral blood mononuclear cells (PBMCs) of 26 primary APS (PAPS), 19 systemic lupus erythematosus-associated APS (SLE/APS) patients and 10 healthy controls. The SLE-related or APS-related single nucleotide polymorphisms (SNP) were analyzed in those patients. Interferon (IFN) score was calculated based on the mRNA expression of Ly6e, Mx1, IFIT1, and IFIT3 in PBMCs. The PBMCs obtained from APS patients were cultured ex vivo following depletion of CD20 positive or negative B cells and the culture supernatants were applied to aPL measurements. Results In PAPS and SLE/APS patients, Th2, Th17, and plasmablasts were increased while regulatory T, memory B, and regulatory B cells were decreased compared to healthy controls. Genetic analysis revealed that the increase of plasmablasts was more pronounced in patients carrying a risk allele of toll like receptor (TLR) 7 SNP rs3853839. The IFN score was significantly higher in the risk allele carriers. Ex vivo experiments showed that aPL were present in the culture supernatant of PBMCs lacking CD20+CD19+ subset, but not in that of cells lacking CD20-CD19+ subset. Conclusions Our data indicate an important role of plasmablasts in the production of aPL. Furthermore, the increase of plasmablasts was associated with TLR 7 and type I IFN, suggesting a common pathophysiology in SLE and APS. Targeting plasmablasts might be a novel immunological therapeutic approach in the treatment of APS.

Role of TLR‑4 in anti‑β2‑glycoprotein I‑induced activation of peritoneal macrophages and vascular endothelial cells in mice

Anti‑phospholipid syndrome (APS) is a systematic autoimmune disease that is associated with presence of antiphospholipid antibodies (aPL), recurrent thrombosis, and fetal morbidity in pregnancy. Toll‑like receptor‑4 (TLR‑4), a member of TLR family, is known to have a fundamental role in pathogen recognition and activation of innate immunity. The β2‑glycoprotein I (β2GPI), a protein circulating in the blood at a high concentration, is able of scavenging lipopolysaccharide (LPS) and clear unwanted anionic cellular remnants, such as microparticles, from the circulation. Our previous study demonstrated that TLR‑4 and its signaling pathways contribute to the upregulation of pro‑coagulant factors and pro‑inflammatory cytokines in monocytes induced by anti‑β2GPI in vitro. The present study aimed to define the roles of TLR‑4 in vivo. C3H/HeN mice (TLR‑4 intact) and C3H/HeJ mice (TLR‑4 defective) were stimulated with an intraperitoneal injection with anti‑β2GPI‑immunoglobulin G(IgG), then peritoneal macrophages and vascular endothelial cells (VECs) were extracted from treated mice, and analyses were conducted on the expression profiles of pro‑inflammatory cytokines and adhesion molecules. The results demonstrated that the expression of pro‑inflammatory cytokines, including tumor necrosis factor‑α (TNF‑α), interleukin (IL)‑1β and IL‑6, in the peritoneal macrophages, and adhesion molecules, including intercellular cell adhesion molecule‑1 (ICAM‑1), vascular cell adhesion molecule‑1 (VCAM‑1) and E‑selectin, in VECs of C3H/HeN mice (TLR‑4 intact) were significantly higher than those of C3H/HeJ mice (TLR‑4 defective). The phosphorylation levels of p38 mitogen‑activated protein kinase (MAPK) and nuclear factor‑κB (NF‑κB) p65 in peritoneal macrophages and VECs from C3H/HeN mice stimulated with anti‑β2GPI‑IgG were significantly increased compared with those from C3H/HeJ mice (TLR‑4 defective). The isotype control antibody (NR‑IgG) had no such effects on peritoneal macrophages and VECs. Furthermore, the inhibitors of TLR‑4, p38 MAPK and NF‑κB may significantly reduce the anti‑β2GPI‑IgG‑induced TNF‑α, IL‑1β and IL‑6 mRNAs expression in the peritoneal macrophages from TLR‑4 intact mice. The results indicated that a TLR‑4 signal transduction pathway is involved in anti‑β2GPI‑IgG‑induced activation of peritoneal macrophages and VECs. This study has provided a basis for subsequent investigations to elucidate the pathological mechanisms underlying anti‑phospholipid syndrome.

Marginal zone lymphoma-associated antiphospholipid antibodies successfully treated with bendamustine rituximab

A 46-year-old man presented with splenomegaly, abdominal adenopathy and profoundly elevated prothrombin time and partial thromboplastin time. He was diagnosed with marginal zone lymphoma (MZL) and small lymphocytic lymphoma, and the abnormal coagulation studies were secondary to the presence of a lupus anticoagulant. Optimal upfront therapy for MZL has not been established, and the incidence of antiphospholipid antibodies (APLA) in this patient population is rare. Following treatment with six cycles of bendamustine and rituximab with 2 years of rituximab maintenance, our patient remained in remission and his coagulation studies normalised. This report describes a case of successful treatment of APLA associated with MZL that resolved after treatment of the lymphoma.

Anticoagulating patients with high-risk acquired thrombophilias

Antiphospholipid syndrome (APS), heparin-induced thrombocytopenia, and paroxysmal nocturnal hemoglobinuria are 3 acquired thrombophilias that carry a high risk of venous and arterial thromboembolism. Management of these conditions has largely included anticoagulation with a vitamin K antagonist after an initial period of a parenteral anticoagulant, for as long as the thrombotic risk is still present. The available evidence for the use of direct oral anticoagulants (DOACs) is limited and primarily consists of case series and cohort studies, which are summarized in this chapter. Randomized trials evaluating DOACs in patients with APS are reviewed. Further research is needed prior to widely adopting DOACs for use in these high-risk acquired thrombophilias; however, there may be selected low-risk subgroups where DOAC use is possible after careful consideration and patient discussion.

Anticoagulating patients with high-risk acquired thrombophilias

Antiphospholipid syndrome (APS), heparin-induced thrombocytopenia, and paroxysmal nocturnal hemoglobinuria are 3 acquired thrombophilias that carry a high risk of venous and arterial thromboembolism. Management of these conditions has largely included anticoagulation with a vitamin K antagonist after an initial period of a parenteral anticoagulant, for as long as the thrombotic risk is still present. The available evidence for the use of direct oral anticoagulants (DOACs) is limited and primarily consists of case series and cohort studies, which are summarized in this chapter. Randomized trials evaluating DOACs in patients with APS are reviewed. Further research is needed prior to widely adopting DOACs for use in these high-risk acquired thrombophilias; however, there may be selected low-risk subgroups where DOAC use is possible after careful consideration and patient discussion.

Thrombotic risk assessment and analytical performance of the chemiluminescent analyzer IDS-iSYS for the detection of anti-cardiolipin and anti-beta 2 glycoprotein I autoantibodies

Patients with antiphospholipid antibodies (APLA) are predisposed to develop thrombosis, however the standardization of anti-cardiolipin (aCL) and anti-beta 2 glycoprotein I (β2-GPI) Ab assays are challenging. Therefore we decided to test the performance of a new chemiluminescent assay (CLIA), and assayed aCL and aβ2-GPI IgG/M in serum from 120 healthy individuals, 108 patients with idiopathic venous thrombosis, 78 patients with antiphospholipid syndrome (APS), and 64 non-thrombotic APLA-carriers using CLIA IDS-iSYS. Very good (aCL/aβ2-GPI IgG) to moderate (aCL/aβ2-GPI IgM) agreement with a commercial and an in house ELISA assay were observed and, in particular, CLIA demonstrated the highest sensitivity in aβ2-GPI IgG detection. Finally, aCL/aβ2-GPI Ab capacity to predict the thrombotic risk was tested showing for CLIA a significant odds ratio (OR) when considering double positivity for aCL/aβ2-GPI IgG, aCL IgG at high levels, and aβ2-GPI IgG at high levels. In conclusion, CLIA improves aβ2-GPI IgG detection and thrombotic risk assessment.

Antibodies to phosphatidylserine/prothrombin (aPS/PT) enhanced the diagnostic performance in Chinese patients with antiphospholipid syndrome

Background:

Increasing evidence has highlighted the role of non-criteria antiphospholipid antibodies (aPLs) as important supplements to the current criteria aPLs for the diagnosis of antiphospholipid syndrome (APS). In this retrospective study, we evaluated the clinical relevance of antibodies to phosphatidylserine/prothrombin (aPS/PT) in Chinese patients with APS.

Methods:

A total of 441 subjects were tested, including 101 patients with primary APS (PAPS), 140 patients with secondary APS (SAPS), 161 disease controls (DCs) and 39 healthy controls (HCs). Serum IgG/IgM aPS/PT was determined by ELISA.

Results:

The levels of IgG/IgM aPS/PT were significantly increased in patients with APS compared with DCs and HCs. IgG and IgM aPS/PT were present in 29.7% and 54.5% of PAPS, and 42.1% and 53.6% of SAPS, respectively. For diagnosis of APS, IgG aCL exhibited the highest positive likelihood ratio (LR+) of 21.60, followed by LA (13.84), IgG aβ2GP1 (9.19) and IgG aPS/PT (8.49). aPS/PT was detected in 13.3% of seronegative PAPS patients and 31.3% of seronegative SAPS patients. LA exhibited the highest OR of 3.64 in identifying patients with thrombosis, followed by IgG aCL (OR, 2.63), IgG aPS/PT (OR, 2.55) and IgG aβ2GP1 (OR, 2.33). LA and IgG aCL were correlated with both arterial and venous thrombosis, whereas IgG aPS/PT and IgG aβ2GP1 correlated with venous or arterial thrombosis, respectively.

Conclusions:

Our findings suggest that the inclusion of IgG/IgM aPS/PT may enhance the diagnostic performance for APS, especially in those in whom APS is highly suspected, but conventional aPLs are repeatedly negative. In addition, IgG aPS/PT may contribute to identify patients at risk of thrombosis.