MEASURING CIRCULATING CYTOKINES

Cytokines, i.e., regulatory proteins derived primarily (but not exclus ively) from cells of the immune system, are receiving increasing atten tion for their influences on physiological processes. This paper outli nes several of the unique characteristics of cytokines and discusses t he pitfalls encountered when measuring them in biological fluids. At p resent, each available assay has a combination of advantages and drawb acks; therefore, investigators must be aware of the trade-offs and cho ose the assay that best addresses their needs. The factors that affect cytokine measurement also influence cytokine activity in vivo; thus t hey are important from a physiological as well as methodological stand point. Moreover, the absolute concentration of a single cytokine is pr obably less important than the balance between that cytokine and its n atural antagonists.