Polymorphisms in <i>FCN</i> genes and their influence on systemic lupus erythematosus susceptibility: a report from Western India

Ficolins, encoded by FCN genes, are key pattern recognition molecules of the lectin complement pathway involved in immune complex clearance, a process often impaired in systemic lupus erythematosus (SLE). Genetic polymorphisms in FCN genes may influence disease susceptibility. However, their functional significance in SLE remains unclear. The present study aimed to investigate the association of selected FCN gene single-nucleotide polymorphisms (SNPs) with SLE, lupus nephritis (LN), and serum ficolin levels in a Western Indian cohort. Seven SNPs in FCN1 (rs2989727, rs1071583), FCN2 (rs7851696, rs17549193, rs7865453, rs17514136), and FCN3 (rs3813800) were genotyped in 200 SLE patients and 200 healthy controls using polymerase chain reaction (PCR) sequence-specific primer and PCR restriction fragment length polymorphism. Serum ficolin-1, -2, and -3 levels were measured using ELISA. Statistical analysis included χ2 test, Kruskal-Wallis test, and logistic regression to assess associations and calculate odds ratios with 95% confidence intervals. The analysis identified significant associations of FCN2 rs7851696, rs7865453, and rs17514136, as well as FCN3 rs3813800, with SLE susceptibility. Among LN patients, FCN1 rs2989727 and rs1071583, FCN2 rs17514136, and FCN3 rs3813800 showed significant associations. FCN3 rs3813800 was significantly associated with ficolin-3 levels, while FCN2 rs7865453 was associated with complement component 1q-circulation immune complex levels. These findings provide novel insight into associations of FCN gene polymorphisms with SLE and LN susceptibility, with genotype-phenotype correlations suggesting their biological relevance. Future longitudinal and mechanistic studies are warranted to validate these associations and explore their therapeutic potential.