Evolution of effectors and receptors of innate immunity

The bony fishes are derived from one of the earliest divergent vertebrate l ineages to have both innate and acquired immune systems. They are considere d by some to be an ideal model to study the underpinnings of immune systems precisely because of their phylogenetic position and the fact that their a daptive immune systems have not been elaborated to the extent seen in mamma ls. By the same token, examination of innate immune systems in invertebrate s and early chordates can provide insight into how homologous systems opera te in fish and higher vertebrates. Herein, we provide an overview of the mo lecular evidence that we hope helps clarify the evolutionary relationships of innate immune molecules identified in bony fishes. The innate immune sys tems being considered include select chemokines (CC and CXC chemokines and their receptors), cytokines (IL-1, IL-8, interferons, TGF-beta, TNF-alpha), acute phase proteins (SAA, SAP, CRP, alpha 2M, and the complement componen ts-C3-C9, MASP, MBL, Bf), NK cell receptors, and molecules upstream and dow nstream of the Toll signaling pathways. (C) 2001 Elsevier Science Ltd. All rights reserved.