Expansion of innate immunity genes in amphioxus (right) compared with the human system (left). Novel domain architectures and (predicted) varied receptor conformations found in amphioxus proteins are expected to increase the specificity of innate immunity in amphioxus. We propose that some TLR-like proteins are localized in the endosome, as also seen in mammals. Domains: TIR (Toll/interleukin-1 receptor) domain, NACHT (NAIP, CIITA, HET-E and TP1), LRR (leucine-rich repeat), CARD (caspase recruitment domain), PYRIN (N-terminal domain of protein pyrin), DD (death domain), DED (death effector domain), SAM (sterile alpha motif) domain, BIR (Baculovirus Inhibitor of apoptosis Repeat).
