UBIQUITOUS INTERLEUKIN-1-ALPHA IN FETAL BOVINE SERUM MAY MISLEAD THE EXPERIMENTAL RESULTS IN-VITRO

Fetal bovine sera (FBS) from several commercial suppliers were fractio nated by gel filtration. Interleukin-1 (IL-1) activity was bioassayed using the IL-1-specific murine T cell line D10(N-4)M. All the sera exa mined contained IL-1-like activity, with molecular weights (Mr) of 30 kDa and 15-10 kDa. Under isoelectric focusing (IEF), the majority of I L-1 activity in either 30 kDa or 15-10 kDa fractions was focused into a position of pl 5. The activity recovered from either IEF or gel filt ration was inhibited by either recombinant human IL-1 receptor antagon ist (rhlL-1ra) or by the antibody against human IL-1 alpha. These biol ogical and physicochemical properties strongly suggest that the active molecules were bovine IL-1 alpha and its precursor. There was no corr elation between the amount of endotoxin and IL-1 activity, Quantificat ion of the fractionated IL-1 indicated its presence in concentrations of 200-5000 pg/ml equivalent to human IL-1. However, high levels of IL -1 were not apparent in unfractionated FBS. Proliferation of T cells i n the presence of FBS absorbed with protein A-Sepharose was greater th an that of cells in original FBS. Therefore, the activity in FBS as a whole appeared to result from the balance between IL-1 and the inhibit ory molecule(s). These results suggest that data obtained from experim ents conducted in the presence of FBS may be influenced by the effect of bovine IL-1.