Calcium-dependent lectin that acts as a pattern recognition receptor (PRR) of the innate immune system: recognizes damage-associated molecular patterns (DAMPs) of pathogen-associated molecular patterns (PAMPs) of bacteria and fungi. The PAMPs include alpha-mannans on C.albicans hypheas and mycobacterial trehalose 6,6'-dimycolate (TDM) (By similarity). Interacts with signaling adapter Fc receptor gamma chain/FCER1G, likely via CLEC4E, to form a functional complex in myeloid cells (PubMed:23921530). Binding of mycobacterial TDM or C.albicans alpha-mannans to this receptor complex leads to phosphorylation of the immunoreceptor tyrosine-based activation motif (ITAM) of FCER1G, triggering activation of SYK, CARD9 and NF-kappa-B, consequently driving maturation of antigen-presenting cells and shaping antigen-specific priming of T-cells toward effector T-helper 1 and T-helper 17 cell subtypes. The heterodimer formed with CLEC6A is active against fungal infection. Functions as an endocytic receptor. May be involved in antigen uptake at the site of infection, either for clearance of the antigen, or for processing and further presentation to T-cells (By similarity). Heterodimer with CLEC4E; disulfide-linked (PubMed:23921530). CLEC4E acts as a bridge for interaction between CLEC4D and FCER1G to form a functional complex (PubMed:23921530). Heterodimer with CLEC6A; this heterodimer forms a pattern recognition receptor (PRR) against fungal infection (By similarity). Expressed in myeloid cells (dendritic cells, macrophages and neutrophils) and B-cells.