Presence and conservation of the immunoglobulin superfamily in insects: current perspective and future challenges

Numerous proteins that contain a bona fide immunoglobulin domain have been identified in the last decade showing that immunoglobulin-like proteins are quite common in metazoans. In particular, recent surveys identified more than 140 immunoglobulin-like proteins in Drosophila melanogaster, Anopheles gambiae and Bombyx mori. A well-studied example of immunoglobulin-like protein is the Drosophila Down syndrome cell adhesion molecule (Dscam) that, accordingly to comparative molecular analyses, showed a high conservation in Diptera, Hymenoptera and Coleoptera, together with a conserved presence of alternative splicing that permitted insects to possess an unsuspected molecular complexity of their innate immune system. At a functional level, immunoglobulin-like proteins seem to be capable of reacting to pathogen challenges and may contribute to the defense against infection so that they are candidates as immune effector molecules in insects. Preliminary findings on insect-borne plant and animal diseases suggest a possible role of the immunoglobulin-like proteins in the vectorial capacity.