The interplay between primary and secondary cytokines. Cytokines involved in the regulation of monocyte recruitment

Cytokines and chemokines play significant roles in the recruitment of leucocytes from the circulation and are therefore crucial determinants of inflammatory reactions and immunity. As knowledge of the actions of these agents and their regulatory mechanisms increases, so does the opportunity to devise pharmacological means of intervening in the activities of these molecules. It is now believed, for instance, that the actions of the classical pro-inflammatory cytokine interleukin (IL)-1 are inhibited by the expression and presentation of a 'decoy' receptor, which acts as a 'molecular trap' for IL-1. There is evidence to suggest that IL-6, formerly considered a purely anti-inflammatory cytokine, also has pro-inflammatory properties. Furthermore, regulation of the chemokine system, which can be achieved by regulating agonist production or altering the expression of chemokine receptors, has recently been demonstrated. These and other new findings, which may prove to have considerable relevance as regards current or future strategies for the treatment of inflammation, infection, neoplasia etc., are presented and discussed in this article.