Role of central nervous system and behaviour in the immune response.

Recent advances in antigen preparation and delivery have led to a renewed interest in vaccination to control infectious disease. However, relatively less attention has been devoted to host factors which affect the outcome of immune responses. There is now increasing acceptance that the central nervous and immune systems interact, and that this can be a bidirectional process. A range of behavioural and psychological states, learned responses and reactions to external stimuli have all been implicated in immune modulation. These interactions may occur via the direct innervation of lymphoid compartments, by paracrine means through the release of mediators from nerves situated in close proximity to cells involved in immunity, or by neuroendocrine signals in the form of hypothalamic, pituitary and peripheral endocrine hormones. These effects may account to some extent for unexplained variability in response to vaccination and disease challenge, through inherited or acquired differences in neuroendocrine or neurotransmitter responses to stress, circadian effects or learned behavioural responses. This review addresses the effects of environmental stimuli and behavioural manipulations on immune outcome and the response to vaccination, and the potential for practical application of these techniques in human and animal disease control and health management.