CLEC4C is a lectin-type cell surface receptor expressed exclusively on plasmacytoid dendritic cells (pDCs) that functions as a pattern recognition receptor in innate immunity. The protein recognizes non-sialylated galactose-terminated biantennary glycans containing the trisaccharide epitope Gal(β1-3/4)GlcNAc(β1-2)Man and binds serum IgG 12. CLEC4C mediates antigen capture and efficiently targets ligands into antigen-processing compartments for T-cell presentation 3. Critically, CLEC4C engagement inhibits type I interferon (IFN-α/β) production in pDCs, a pathway central to systemic lupus erythematosus (SLE) pathogenesis 31. Clinically, CLEC4C (also known as BDCA2) represents a validated therapeutic target. Anti-CLEC4C monoclonal antibodies, such as litifilimab, suppress pDC-derived type I interferon through both Fc-dependent and Fc-independent mechanisms 4. Phase 2 trials demonstrate litifilimab efficacy in cutaneous lupus erythematosus and systemic lupus erythematosus, reducing skin disease activity and joint inflammation 567. CLEC4C gene expression correlates with circulating pDC numbers and serves as a biomarker for pDC quantification 8. Loss-of-function CLEC4C variants impair cell surface transport, contributing to neurodegenerative disease susceptibility 9.