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Distinct effects of complement C4A and C4B copy number in Systemic Sclerosis serological and clinical subtypes

Martínez-López, Javier; Rangel-Peláez, Carlos; Rodriguez-Martin, Inmaculada; Guillen-Del-Castillo, Alfredo; Simeón-Aznar, Carmen P; Callejas, José L; International SSc Group; PRECISESADs Clinical Consortium; ... Kerick, Martin; + view all (2025) Distinct effects of complement C4A and C4B copy number in Systemic Sclerosis serological and clinical subtypes. Arthritis & Rheumatology 10.1002/art.43433. (In press). Green open access

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Abstract

OBJECTIVE: Complement component 4 (C4), encoded by C4A and C4B within the major histocompatibility complex (MHC) on chromosome 6, regulates the immune response and clears immune complexes. Variable copy number (CN) of C4 genes and retroviral HERV-K element influence its function. Given the relationship of C4 CN with SSc risk, we assessed associations with SSc clinical and serological subtypes. METHODS: We compared imputed C4 CNs across SSc subgroups (4,049 ACA+; 2,200 ATA+; 577 ARA+; 1,078 triple negative patients (TN); 6,295 limited cutaneous (lcSSc); 2,946 diffuse cutaneous (dcSSc)) and 17,991 controls. We evaluated associations with SSc subtypes, identifying C4-independent HLA alleles. RESULTS: Lower C4 CN and higher HERV-K CN were associated with increased risk in all SSc subgroups. ATA+ patients showed the strongest association, particularly with C4A (OR=1.88) and differences in C4A CN association were more pronounced between autoantibody subgroups (ATA+ vs ACA+, p = 4x10-11) than between clinical subgroups (dcSSc vs lcSSc, p = 1x10-4). In ACA+ patients, only low C4B CN showed a significant association to SSc risk (p=1.23x10-5). We also observed sex-biased associations: dcSSc, ATA+ and ARA+ males showed stronger effects for C4A and ACA+ and lcSSc females for C4B. Finally, our results suggest that the HLA alleles associated with SSc subgroups are independent of C4 CN. CONCLUSION: This study highlights distinct genetic contributions of C4A and C4B in SSc subtypes susceptibility. Our findings suggest that lower C4 CNs, particularly C4A, increase the risk of the severe dcSSc subtype, potentially through a mechanism involving immune complex clearance.

Type: Article
Title: Distinct effects of complement C4A and C4B copy number in Systemic Sclerosis serological and clinical subtypes
Location: United States
Open access status: An open access version is available from UCL Discovery
DOI: 10.1002/art.43433
Publisher version: https://doi.org/10.1002/art.43433
Language: English
Additional information: This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License (http://creativecommons.org/licenses/by-nc/4.0/), which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.
UCL classification: UCL
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences > Div of Medicine
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences > Div of Medicine > Inflammation
URI: https://discovery.ucl.ac.uk/id/eprint/10218365
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