Lipoxins LXA and LXB are potent inhibitors of neutrophil microbicidal activity. PAF directly primes superoxide generation and elastase release. The major ''stress hormones'' are involved in the regulation of inflammation at both the systemic and, perhaps, local levels. The bidirectional interactions of cytokines and neurotransmitters with nervous and immune cells, respectively, provide a means of indirect chemical communication between the neuroendocrine and immune systems. From the neuroendocrine hormones mainly growth hormone, prolactin, -endorphin, glucocorticoids and catecholamines are involved in the neutrophil regulation.
Growth hormone primes the oxidative burst of human neutrophils.
Prolactin , which shares considerable functional and structural similarities with growth hormone, is also a strong immunopotentiating agent. Prolactin primes the oxidative burst of neutrophils and macrophages to the same intensity as that induced by growth hormone. Although glucocorticoids and opioids may enhance some immune responses at very low concentrations, they are generally considered to be immunosuppressive. These contrasting responses may be controlled by the presence of multiple receptors for the same mediator that are coupled to stimulatory and inhibitory pathways. In fact, containment of the stress response may be the principal role of glucocorticoids.