Figure 2 - Glycan-binding proteins involved in pathogen interaction leading to antigen presentation and signaling in APC.

Many C-type lectins and several siglecs (Siglecs 1, 5, 7 and H) are pathogen recognition receptors that interact with specific glycan structures on these pathogens, such as Lewis^x,y, GlcNAc, high-mannose structures, sialic acids and GalNAc, and mediate internalization and enhanced antigen processing and presentation by MHC class I and II. Soluble galectins can interact with pathogens, forming lattices and initiating innate immune responses. Pathogen recognition by C-type lectins and siglecs expressed on APCs can lead to various intracellular signaling processes and modulate TLR signaling or elicit signaling independently of TLR activation. Galectins can interact with certain glycoproteins expressed by APCs, thereby modulating APC maturation and cytokine production. Gal, galectin; MyD88, a common adaptor protein involved in TLR signaling.