| 1. |
- Grosso, Giorgia, et al.
(författare)
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The Complex Relationship between C4b-Binding Protein, Warfarin, and Antiphospholipid Antibodies
- 2021
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Ingår i: Thrombosis and Haemostasis. - : Georg Thieme Verlag KG. - 0340-6245 .- 2567-689X. ; 121:10, s. 1299-1309
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Tidskriftsartikel (refereegranskat)abstract
- Background Low levels of total C4b-binding protein (C4BPt), a circulating inhibitor of the classical/lectin complement pathways, were observed in patients with antiphospholipid antibodies (aPLs) and during warfarin treatment. Objectives To investigate the associations between aPL and C4BPt in patients with persistently positive (++) aPL, with/without clinical manifestations and systemic lupus erythematosus (SLE), and in controls. Furthermore, we explored the impact of anticoagulation on C4BPt and in relation to complement activation. Methods In a cross-sectional design we investigated defined subgroups: primary (p) antiphospholipid syndrome (APS, N =67), aPL++ individuals without clinical manifestations (aPL carriers, N =15), SLE-aPL++ ( N =118, among them, secondary [s] APS, N =56), aPL negative (-) SLE (SLE-aPL-, N =291), and 322 controls. Clinical characteristics, including treatment, were tabulated. C4BPt was determined with a magnetic bead method. Complement proteins (C1q, C2, C3, C4, C3a, C3dg, sC5b-9, factor I [FI]) were measured. A mediation analysis was performed to decompose the total effect of aPL++ on C4BPt into the direct and indirect effects of aPL++ through warfarin. Results Overall, C4BPt is 20% decreased in aPL++ patients, regardless of SLE, APS, clinical manifestations, and aPL profile. C4BPt levels associate positively with complement proteins C1q, C2, C3, and C4, and negatively with complement activation product C3dg. In the SLE group, warfarin treatment contributes to approximately half of the C4BPt reduction (9%) Conclusion Both aPLs and warfarin are associated with C4BPt reduction. Complement activation in aPL++ patients may partly be explained by impaired inhibition through depressed C4BPt levels. Further studies are needed to understand the clinical implications.
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| 2. |
- Lindelöf, Linnea, et al.
(författare)
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62 Acquired ficolin-3 deficiency in patients with Systemic Lupus Erythematosus
- 2023
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Ingår i: Immunobiology. - : Elsevier. - 0171-2985 .- 1878-3279. ; 228:5, s. 152515-152515
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Tidskriftsartikel (refereegranskat)abstract
- Background: Ficolin-3 is the main initiator of the lectin pathway in humans. Case reports of ficolin-3 deficient patients have suggested that ficolin-3 deficiency may be enriched in patients with Systemic Lupus Erythematosus (SLE), a systemic autoimmune disease where complement plays an important role. Therefore, this study aimed to investigate the activity levels of ficolin-3 and to identify potential ficolin-3 deficient individuals in two Swedish SLE cohorts.Methods: Serum or plasma samples from SLE patients (n=810) and matched controls (n=566) were collected from the Karolinska Institute (KI) and Umeå University Hospital. The ficolin-3 activity levels were measured by an in-house developed functional ELISA with a pooled normal human serum sample as a reference. Serial samples were analyzed for ficolin-3 deficient patients when available. Sequencing data were analyzed for FCN3 frame-shift mutation +1637delC (rs532781899) and other potential loss-of-function (LoF) variants.Results: This screening revealed that the level of ficolin-3 activity varies largely in patients with SLE. The activity levels also show that SLE patients seem to generally have elevated ficolin-3 activity compared to the control group (p<0.0001). Out of 810 patients with SLE, four patients were determined to be ficolin-3 deficient. For two of these patients, the ficolin-3 activity was at normal levels at the time of diagnosis and thereafter depleted over time, indicating an acquired deficiency. For deficient patients, no or very low ficolin-3 protein levels and no lectin pathway-dependent complement activation could be detected. Autoantibodies against ficolin-3 were not detectable. No patients were homozygous for the +1637delC frameshift mutation, whereas in total 10 patients were determined to be heterozygous carriers. These heterozygous patients displayed lower levels of ficolin-3 activity but did not include the deficient patients. Additional possible LoF variants were analyzed but none were enriched in either patients or controls.Conclusions: Contrary to the classical pathway of the complement system we show that genetic ficolin-3 deficiency is not a risk factor for SLE. Instead, acquired ficolin-3 deficiency was observed in a subgroup of SLE patients, possibly due to a potent activation of the lectin pathway that depleted ficolin-3 plasma levels in these individuals.
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| 3. |
- Lindelöf, Linnea, et al.
(författare)
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A survey of ficolin-3 activity in Systemic Lupus Erythematosus reveals a link to hematological disease manifestations and autoantibody profile
- 2024
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Ingår i: Journal of Autoimmunity. - : Elsevier. - 0896-8411 .- 1095-9157. ; 143
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Tidskriftsartikel (refereegranskat)abstract
- The complement system plays a central role in the pathogenesis of Systemic Lupus Erythematosus (SLE), but most studies have focused on the classical pathway. Ficolin-3 is the main initiator of the lectin pathway of complement in humans, but its role in systemic autoimmune disease has not been conclusively determined. Here, we combined biochemical and genetic approaches to assess the contribution of ficolin-3 to SLE risk and disease manifestations. Ficolin-3 activity was measured by a functional assay in serum or plasma samples from Swedish SLE patients (n = 786) and controls matched for age and sex (n = 566). Genetic variants in an extended 300 kb genomic region spanning the FCN3 locus were analyzed for their association with ficolin-3 activity and SLE manifestations in a Swedish multicenter cohort (n = 985). Patients with ficolin-3 activity in the highest tertile showed a strong enrichment in an SLE cluster defined by anti-Sm/DNA/nucleosome antibodies (OR 3.0, p < 0.001) and had increased rates of hematological disease (OR 1.4, p = 0.078) and lymphopenia (OR = 1.6, p = 0.039). Genetic variants associated with low ficolin-3 activity mapped to an extended haplotype in high linkage disequilibrium upstream of the FCN3 gene. Patients carrying the lead genetic variant associated with low ficolin3 activity had a lower frequency of hematological disease (OR 0.67, p = 0.018) and lymphopenia (OR 0.63, p = 0.031) and fewer autoantibodies (p = 0.0019). Loss-of-function variants in the FCN3 gene were not associated with SLE, but four (0.5 %) SLE patients developed acquired ficolin-3 deficiency where ficolin-3 activity in serum was depleted following diagnosis of SLE. Taken together, our results provide genetic and biochemical evidence that implicate the lectin pathway in hematological SLE manifestations. We also identify lectin pathway activation through ficolin-3 as a factor that contributes to the autoantibody response in SLE.
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| 4. |
- Svenungsson, Elisabet, et al.
(författare)
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Complement deposition, C4d, on platelets is associated with vascular events in systemic lupus erythematosus
- 2020
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Ingår i: Rheumatology. - : Oxford University Press. - 1462-0324 .- 1462-0332. ; 59:11, s. 3264-3274
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Tidskriftsartikel (refereegranskat)abstract
- Objective. Complement components, including C4d, can be found on activated platelets, a process associated with vascular disease in SLE. We investigated whether platelet C4d (PC4d) adds additional value to traditional and known lupus-associated risk factors when identifying SLE patients with vascular disease. Methods. This cross-sectional study included 308 well-characterized SLE patients and 308 matched general population controls. PC4d deposition was analysed using flow cytometry. Values >95% of controls were considered as PC4d positive (+). aPL were determined by Luminex, and the LA test was performed by DRVVT. History of vascular disease (composite and as separate outcomes) was defined at inclusion. Results. SLE patients had increased PC4d deposition as compared with population controls (50 vs 5%, P < 0.0001). PC4d+ positively associated with any vascular events, and separately with venous and cerebrovascular events, and also with all investigated aPL profiles. The association for any vascular event remained statistically significant after adjustment for traditional and SLE-associated risk factors (odds ratio: 2.3, 95% CI: 1.3, 4.3, P = 0.008). Compared with patients negative for both PC4d and LA, patients with double positivity were more likely to have vascular disease (odds ratio: 12.3, 95% CI: 5.4, 29.3; attributable proportion due to interaction 0.8, 95% CI: 0.4, 1.1) Conclusion. PC4d+ is associated with vascular events in SLE, independently of traditional and SLE-associated risk factors. Concurrent presence of PC4d and LA seem to interact to further increase the odds for vascular events. Prospective studies should examine whether the aPL/PC4d combination can improve prediction of vascular events in SLE and/or APS.
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