CLEC4D is a calcium-dependent C-type lectin that functions as a pattern recognition receptor in innate immunity, recognizing damage-associated and pathogen-associated molecular patterns from bacteria and fungi, including alpha-mannans from Candida albicans and mycobacterial trehalose 6,6'-dimycolate [PubMed:23602766, PubMed:23911656]. Upon ligand binding, CLEC4D forms a signaling complex with the Fc receptor gamma chain, leading to phosphorylation of immunoreceptor tyrosine-based activation motifs and activation of downstream kinases SYK, CARD9, and NF-κB, ultimately promoting dendritic cell maturation and T-helper 1 and T-helper 17 cell differentiation [PubMed:23602766, PubMed:23911656]. The receptor also functions in endocytosis, facilitating antigen uptake and processing for T-cell presentation [PubMed:14971047]. CLEC4D expression is elevated in several disease contexts: it is upregulated in obese Prader-Willi syndrome patients and correlates with body mass index [PubMed:40105403], serves as a diagnostic biomarker for coronary artery disease progression in type 1 diabetes [PubMed:37075605], and is identified as a monocyte-associated therapeutic target in tuberculosis with demonstrated causal association to elevated TB risk [PubMed:40618704]. Recent evidence suggests CLEC4D may mediate age-related lung cancer risk [PubMed:37745724]. These findings position CLEC4D as both a critical regulator of antifungal and antibacterial responses and an emerging biomarker in metabolic and infectious disease pathogenesis.