these data concern two major avenues of research : the evidence that brain-controlled , behavioral parameters can modulate the response of immunocompetent cells , and an increasing awareness that a number of chemical signals - neurotransmitters , hormones or mediators of immunity - are not , as previously believed , specific of given sets of tissues or of functions , but that , on the contrary , they can be produced and recognized by cellular elements belonging to any of those three systems .
C0006104
brain
C0004927
behavioral