Is the adaptive immune system an evolutionary off-shoot of the vertebrate nervous system?
As though to tickle the imagination, it appears that the acquisition of RAG genes may have coincided with the elaboration of neural crest and tissues derived from it, such as jaws, at a time of increasing complexity of the nervous system. The possible relevance of this becomes evident when we consider insights suggested first by Bill Hildemann and his associates (Hildemann et al., 1979), who drew attention to the fact that the vertebrate immune and nervous systems share the properties of specific recognition, memory and the abilities to mount and target aggressive responses. A growing number of “neuro”-transmitters are now known to be made by and are active in the immune system (Schauenstein et al., 2000), and a growing number of “cytokines” are made by and active in the nervous system (Dunn, 2000). Indeed, it has been convincingly established that neuro-immune cross-talk is essential to homeostasis throughout the vertebrates. What is most intriguing here is that at least some of the s
