Measuring circulating cytokines

Abstract

Cytokines, i.e., regulatory proteins derived primarily (but not exclusively) from cells of the immune system, are receiving increasing attention for their influences on physiological processes. This paper outlines several of the unique characteristics of cytokines and discusses the pitfalls encountered when measuring them in biological fluids. At present, each available assay has a combination of advantages and drawbacks; therefore, investigators must be aware of the trade-offs and choose the assay that best addresses their needs. The factors that affect cytokine measurement also influence cytokine activity in vivo; thus they are important from a physiological as well as methodological standpoint. Moreover, the absolute concentration of a single cytokine is probably less important than the balance between that cytokine and its natural antagonists.

Epinephrine inhibits tumor necrosis factor-alpha and potentiates interleukin 10 production during human endotoxemia.

“…On day 2, arterial blood was obtained at 6:00 a.m. (i.e., directly before the start of the infusion of epinephrine in the EPI-3 group or the start of saline infusion in the control group) ( t ϭ Ϫ 3 h), directly before the injection of endotoxin ( t ϭ 0 h), and 0.5, 1, 1.5, 2, 3, 4,5,6,8,12, and 24 h thereafter. All blood samples (except samples for leukocyte counts) were centrifuged at 4 Њ C for 20 min at 1,600 g and stored at Ϫ 70 Њ C until assayed.…”

“…Anticoagulation was obtained using sterile heparin (Elkins-Sinn Inc., Cherry Hill, NJ) (10 U/ml blood, final concentration). Heparin was chosen as anticoagulant rather than EDTA in whole blood experiments, since EDTA has been reported to inhibit cell function in bioassays and to inhibit the production of TNF (12). Incubation of heparinized whole blood in the absence of LPS did not result in detectable cytokine production.…”

“…It was therefore possible that epinephrine inhibits LPS-induced TNF production in whole blood at least in part by enhancing the release of IL-10. To test this hypothesis, we incubated whole blood for various time periods (4,8,12, and 16 h) with LPS (10 ng/ml) in the presence or absence of epinephrine (10 Ϫ6 M), a neutralizing anti-IL-10 mAb (25 g/ml) or an equivalent amount of an irrelevant isotype-matched control mAb. Anti-IL-10 potentiated LPSinduced TNF production, an effect that became significant after incubations of whole blood for 8 h or longer (Table I).…”

T-Helper-2 Cytokine Responses to Sj97 Predict Resistance to Reinfection withSchistosoma japonicum

“…Current evidence suggests that the Th2/Th1 paradigm may oversimplify cellular immunologic phenomena, thus necessitating analysis of individual cytokines within the context of their potential antagonists (11,15,23). Because of potential antagonism between Th2 and Th1 cytokines, we hypothesized that the balance between individual cytokines made in response to S. japonicum vaccine candidates would more reliably predict potentially protective responses in vivo (11).…”

“…Using a longitudinal treatment-reinfection study design, we assessed the relationship between cytokine responses to a soluble adult worm extract (SWAP), Sj97, Sj22.6, and Sj67, measured 4 weeks after treatment with PZQ, and resistance to reinfection over an 18-month follow-up period. Because assessing individual cytokines may oversimplify cellular immunologic phenomena in part due to potential antagonism between Th2 and Th1 cytokines (11,15,23), we also evaluated the relationship between antigen-specific cytokine ratios and reinfection. We tested the hypothesis that a Th2-type cytokine balance in response to these vaccine candidates would predict a longer time to reinfection and lower intensity of reinfection.…”