Another prominent model of ecdysozoan immunity is Drosophila (Lemaitre and Hoffmann, 2007) , but increasingly other insect are studied as well, such as mosquitoes because of their role in transmitting human parasites (Bartholomay et al., 2010) . Insects have dedicated immune cells such as plasmatocytes and lamellocytes that circulate through their open circulatory system and phagocytose or encapsulate foreign objects. The Drosophila immune system also shows evidence of gene loss: it lacks the C3-like complement component and NLR homologs found in cnidarians. Their TLRs are different from those of vertebrates in that they do not engage microbial ligands directly. Of their nine TLR genes, only one or two function in immunity, activating NF-κB signaling pathways in the fat body to produce AMPs (Lemaitre FIGURE 1 | An overview of some of the novel features associated with immune responses of representatives of major animal lineages (see text for details). TLR, Toll-like receptor; AMP, antimicrobial peptide; Dscam, Down syndrome cell adhesion protein; VCBPs, variable region-containing chitin-binding proteins; NLRs, intracellular NOD-like receptors; LRR, leucine-rich repeat; IgSF, immunoglobulin superfamily; Ab, antibodies; TCR, T cell receptor; MHC, major histocompatibility complex.