Many of them including hematopoietic growth factors and pyrogens have shown to be potent neutrophil priming agents. Cytokines also increase the microbiostatic and killing capacities of neutrophils against bacteria, protozoa and fungi. Furthermore, some cytokines prolong neutrophil survival. Along to cytokines other mediators, including bioactive lipids, neuroendocrine hormones, histamine, and adenosine, are also involved in the regulation of neutrophil activation. Bioactive lipids originate mainly from arachidonic acid which is an abundant constituent of neutrophil membranes.
Arachidonic acid is metabolized to prostaglandins, leukotrienes and lipoxins.
LTB is a strong neutrophil chemoattractant that may play a role in the priming process. Vasoactive leukotrienes LTC , LTD and LTE increase microvascular permeability and may contribute to ischemia-reperfusion injury. 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.