Pathogen recognition is a fundamental step in host immune response and survives against infections. Pathogen recognition happens by host cell surface receptor which induces downstream immune responses such as opsonization, phagocytosis. Among that glycan-binding receptor in C-type lectin superfamily form recognition molecules which are crucial to innate immunity. Many C-type lectins found in pathogen bind to glycan array, but host cell doesn't have so it makes distinguish self and non-self. However, some pathogen uses this selective recognition for primary infection and subsequent proliferation in a host. DC-SIGN(CD209) initially dendritic cell-specific ICAM-3-grabbing nonintegrin is one of the C-type lectin family dendritic cell surface receptor which binds with pathogen glycan. DC-SIGN can bind with two classes of carbohydrate structures: N-linked high mannose oligosaccharides, fucosylated oligosaccharides. Crystal structure of CRD from DC-SIGN with oligosaccharide reveal CRD forms 1-to-1 complex with high-mannose oligosaccharides. Surface force apparatus(SFA) is used to quantify interaction force of cell surface receptor and glycans on the target membrane. This kind of force measurements can quantify variations in the adhesion energy between DC-SIGN with ligand density which further reveal the role of ligand spacing in the multivalent interactions of CRDs with ligand. By SFA, binding-site geometry and flexibility in DC-SIGN demonstrated and calcium contributions for Dendritic cell receptors on carbohydrate recognition proved.