The effect of cytokines on the in-vitro erythropoietin bioassay

The effects of various concentrations of granulocyte macrophage colony stimulating factor (GM-CSF), gamma interferon (gamma IFN) and interleukins 1 alpha (IL-1 alpha), 1 beta (IL-1 beta) and 3 (IL-3) on the anaemic mouse spleen cell bioassay for erythropoietin (EPO) were investigated. Addition of IL-3 and GM-CSF at various concentrations had no effect on EPO stimulated 3H thymidine incorporation. However the addition of IL-1 alpha, IL1-beta and gamma IFN (3.3 x 10(-8) gl-1) caused a significant (P < 0.01) inhibition of EPO stimulated thymidine incorporation. This suggests that the EPO bioassay may be influenced by variable levels of some inflammatory cytokines in serum. Previous studies have shown that the bioassay is influenced by serum transferrin levels and thus serum immunoassays remain the technique of choice for specific estimates of EPO. Since EPO bioassays are not specific, they should be reserved for situations in which an estimate of the total erythropoietic activity of serum is required.