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 interle ukins 1 alpha(IL-1 alpha), 1 beta (IL-1 beta) and 3 (IL-3) on the anae mic mouse spleen cell bioassay for erythropoietin (EPO) were investiga ted. Addition of IL-3 and GM-CSF at various concentrations had no effe ct on EPO stimulated H-3 thymidine incorporation. However the addition of IL1-alpha, IL1-beta and gamma IFN (3.3 x 10(-8) gl(-1)) caused a s ignificant (P < 0.01) inhibition of EPO stimulated thymidine incorpora tion. This suggests that the EPO bioassay may be influenced by variabl e levels of some inflammatory cytokines in serum. Previous studies hav e shown that the bioassay is influenced by serum transferrin levels an d 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 erythropoie tic activity of serum is required.