FCN2 encodes ficolin-2, a calcium-dependent lectin that functions as a pattern recognition receptor in innate immunity by initiating the lectin pathway of complement activation 1. The protein specifically recognizes and binds carbohydrates including N-acetylglucosamine, phosphocholine, and lipoteichoic acid on pathogen surfaces, leading to activation of MASP1 serine protease and subsequent complement cascade activation that promotes phagocytosis and pathogen clearance. FCN2 exhibits significant genetic polymorphisms that affect both protein expression levels and functional capacity 2. Promoter region polymorphisms at positions -986, -602, and -4 influence serum ficolin-2 concentrations, while structural variants in the fibrinogen-like domain alter carbohydrate binding affinity 2. These functional variants show distinct geographical distribution patterns across populations 3. Clinically, FCN2 polymorphisms have been associated with rheumatic fever susceptibility, with certain genotypes conferring protective effects 4. The protein also serves as a biomarker in neurological conditions, with CSF ficolin-2 levels identified as part of protein signatures that predict disease progression in multiple sclerosis 1. Additionally, ficolin-2 functions as an endocrine factor facilitating inter-organ communication in cardiometabolic disorders 5.