BAYNE, C.J.: Immuno-competence before the Paleozoic: how distinctive?

In February 2002, a Keystone Symposium will be addressed by an eminent immunologist on the topic: Is adaptive immunity absolutely dependent on innate immunity? This reflects the phenomenal recent growth in appreciation for the innate arms of immune systems, and the realization that adaptive (lymphoid) immunity is an evolutionary neophyte, acquired by metazoans contemporaneously with “RAG” genes and jaws in Silurian times, some 440 (perhaps 475) million years ago (mybp). What features characterized the innate immune systems in those jawless (pre-gnathostome) animals? This talk, focusing on immuno-competence in molluscan species, provides a perspective on the variety of internal defense mechanisms that had evolved in this phylum well before the end of the Precambrian some 550 mybp. Consistent with the comparative theme, the talk addresses those features that distinguish immuno-competence at such an intermediate level of phylogeny from immuno-competence in modern mammals. In doing so, the talk explores what more had to be in place before adaptive immunity could appear and diversify to become the most impressive system that it is today.