Figure 1.

TLRs and scavenger receptors required for cryptococcal PAMPs. Cryptococcus species contain a large polysaccharide capsule made up of GXM and GalXM. Extracellular receptors present in myeloid cells recognize GXM and GalXM via TLRs. TLR4 forms heterodimers with other extracellular receptors, including CD14, in order to detect capsular polysaccharides. TLR2, CD11b, and CD18 are also able to detect the capsule. Intracellular phagosomal TLR9 recognizes unmethylated CpG motifs of Cryptococcus. The NLR member NLRP3 is crucial for processing internalized cryptococci. Following the recognition of cryptococcal PAMPs, the adaptor molecule MyD88 is essential for the induction of pro-inflammatory mediators. Dashed lines represent various MyD88-dependent and independent signaling pathways required for pro-inflammatory mediator activation. ?? = unknown cryptococcal ligand for MARCO receptor.