rs1885013 — RAD51B RAD51B Rheumatoid Arthritis Variant

RAD51B — When DNA Repair Genes Shape Immune Vulnerability

RAD51B¹¹ RAD51B
RAD51 paralog B, a member of the RAD51 family of proteins essential for repairing DNA double-strand breaks through homologous recombination is best known as a genome guardian — a protein that physically handles the most dangerous type of DNA damage a cell can experience. rs1885013 is an intronic variant within RAD51B on chromosome 14q24.1, sitting within a locus that genome-wide association studies have now linked to both asthma susceptibility and rheumatoid arthritis risk. The same DNA repair gene influencing two seemingly unrelated inflammatory diseases points to a shared biological thread: the role of genomic stability in immune cell function.

The Mechanism

RAD51B is one of five RAD51 paralogs (alongside RAD51C, RAD51D, XRCC2, XRCC3) that form the Rad51B-Rad51C-Rad51D-XRCC2 complex²² Rad51B-Rad51C-Rad51D-XRCC2 complex
This four-protein complex is required for homologous recombination repair of DNA double-strand breaks and is particularly active in S-phase cells undergoing replication stress. rs1885013 falls within an intron and has no direct effect on protein sequence. Instead, it is a proxy for regulatory variation at this locus — either tagging an as-yet-uncharacterized regulatory element affecting RAD51B expression in immune cell subsets, or marking a causal variant in linkage disequilibrium.

The connection between RAD51B and immune function is supported by mechanistic data. Lymphocytes in rheumatoid arthritis patients show elevated RAD51B mRNA expression relative to healthy controls³³ elevated RAD51B mRNA expression relative to healthy controls
Galita et al. 2024 detected significantly elevated RAD51B gene expression in peripheral blood mononuclear cells from RA patients, and RA patients carrying risk variants in RAD51B demonstrate impaired repair of DNA double-strand breaks in lymphocytes — with an OR of 73.4 for deficient repair in those carrying risk haplotypes. Activated immune cells — including T and B lymphocytes undergoing clonal expansion during an allergic or autoimmune response — produce high levels of reactive oxygen species that damage DNA. When RAD51B-dependent repair is subtly altered, these cells may accumulate genomic instability, potentially prolonging activation or altering differentiation decisions in ways that amplify allergic and inflammatory responses.

The opposing risk directions at this locus for asthma (G allele risk) versus rheumatoid arthritis (A allele risk) are consistent with the well-documented genetic trade-off between atopic/type-2 inflammatory diseases and autoimmune/type-1 diseases at several shared immune loci. This immunological seesaw⁴⁴ immunological seesaw
The inverse relationship between atopic disease susceptibility and autoimmune disease susceptibility at the same loci reflects opposite polarization of immune responses — type 2 (atopic) vs type 1 (autoimmune) — at shared genetic control points is a recurrent finding in large GWAS studies.

The Evidence

The asthma association was established in a large GWAS by Ferreira et al. AJHG 2019⁵⁵ Ferreira et al. AJHG 2019
Genetic Architectures of Childhood- and Adult-Onset Asthma Are Partly Distinct; UK Biobank n=447,628; validation in 23andMe n=262,767. rs1885013 achieved genome-wide significance for both childhood-onset asthma (OR 1.085, p=3×10⁻²⁵) and adult-onset asthma (OR 1.056, p=3×10⁻¹³), placing it among the robustly replicated asthma loci. Each copy of the G allele increases asthma susceptibility additively.

The rheumatoid arthritis association at this locus was initially identified by McAllister et al. Arthritis Rheum 2013⁶⁶ McAllister et al. Arthritis Rheum 2013
meta-GWAS of 17,581 RA cases and 20,160 controls; proxy SNP rs911263 in RAD51B p=4×10⁻⁸, OR 0.89, and confirmed in the Ishigaki et al. Nature Genetics 2022⁷⁷ Ishigaki et al. Nature Genetics 2022
multi-ancestry GWAS of 276,020 samples from five ancestral groups; 124 loci including RAD51B mega-analysis. Mechanistic studies by Galita et al. 2024⁸⁸ Galita et al. 2024
45 RA patients vs 45 healthy controls; bleomycin comet assay of DNA double-strand break repair efficiency demonstrated that RA patients with RAD51B risk variants show dramatically impaired DNA damage repair in lymphocytes, with OR 73.4 for deficient repair in RAD51B risk haplotype carriers. Zhi et al. Sci Rep 2017⁹⁹ Zhi et al. Sci Rep 2017
965 RA cases, 2,511 controls; Han Chinese population confirmed the association using the proxy SNP rs911263 (OR 0.64 for the protective allele, p=4.8×10⁻⁵) and additionally found the protective allele associated with reduced joint erosion severity.

Evidence level is classified as moderate: the asthma and RA GWAS associations are robustly replicated and genome-wide significant, but the functional mechanism (which specific regulatory element drives the effect and in which immune cell type) has not yet been characterized for rs1885013 itself.

Practical Actions

For GG homozygotes — who carry two copies of the G risk allele (~10% of Europeans, ~1% of East Asians) — the asthma susceptibility signal is strongest. The actionable focus is monitoring for early asthma symptoms and reducing known triggers that stress airway epithelium. Given that RAD51B is also a cancer susceptibility gene (breast, pancreatic), GG carriers with a family history of these cancers should ensure they receive standard cancer screening.

For AG heterozygotes — present in about 41% of Europeans — asthma risk is modestly elevated. Standard allergen management and awareness of asthma symptoms remain appropriate.

For AA homozygotes — the most common genotype (~50% of Europeans) — asthma risk through this locus is not elevated. However, the A allele is associated with modest RA susceptibility, and those with a personal or family history of RA should ensure they meet standard clinical monitoring thresholds.

Interactions

RAD51B does not act alone in DNA repair. It forms an obligate complex with RAD51C (encoded by PALB2 partner), and both are part of the broader homologous recombination network. Functional overlap exists with RAD51 itself (rs7180135, rs1801321) and other paralogs (XRCC2, XRCC3, RAD51D). In RA patients, combinatorial analysis shows that co-carrying risk variants at multiple DNA repair loci (RAD51B + RAD51 + NBS1) further amplifies the risk of deficient lymphocyte repair.

The opposing-direction association pattern at rs1885013 (G allele protective for RA, A allele protective for asthma) raises the possibility of compound effects in individuals carrying risk alleles at both this locus and independent RA or atopic loci. Cross-category compound actions should be considered between this SNP and pathway partners in the autoimmune-tolerance and allergy-atopic categories if a user carries GG at this locus plus RA-specific risk alleles elsewhere.