Bovine serum albumin preparations enhance in vitro production of tumor necrosis factor alpha by murine macrophages

Abstract

Tumor necrosis factor alpha (TNF-alpha) is most commonly produced by macrophages stimulated by lipopolysaccharide (LPS). The present study shows that BSA in place of FBS in RPMI 1640 medium accelerated the rate of LPS-induced TNF-alpha production by resident peritoneal macrophages from BALB/c mice when compared to LPS in serum free medium. Using 10 or 100 ng LPS/ml and 100 U IFN-gamma/ml in RPMI 1640 medium plus 0.5% BSA, both cytoplasmic TNF-alpha mRNA and TNF-alpha precursor and extracellular TNF-alpha production by mouse macrophages were increased when compared to stimulation by LPS plus IFN-gamma in medium without BSA and FBS. The level of TNF-alpha produced was shown to be related to the BSA concentration. Medium containing BSA but no LPS also stimulated macrophages to produce TNF-alpha, but BSA's TNF-alpha inducing activity varied among different lots and was not blocked by polyclonal antibody to BSA. This effect appeared to be associated with the presence of immunoglobulin in BSA products. Confirmation that BSA activity was not due to LPS contamination was achieved by testing macrophages from LPS-nonresponder C3H/HeJ mice, as well as testing TNF-alpha induction in the presence of polymyxin B (10 micrograms/ml), an LPS inhibitor.