Developmental immune activation programs adult behavior: insight from research on birds.

Immune activation early in life can program adult behavioral expression. Previous research on birds has documented effects of parasite exposure and immune challenges early in life on dispersal, song, personality, learning and feather pecking. However, the mechanisms responsible for mediating these programming effects are unknown. Candidate brain regions that may be most sensitive include the hippocampus and HVC. Without an understanding of mechanism, it is difficult to assess if programmed behaviors represent pathological side effects or behavioral modifications with benefits to either hosts or parasites. Future research on birds promises to provide novel insight into the adaptive value of programming effects of early life immune activation and the capacity for selection to buffer hosts against negative effects.