“…From a cell biological perspective, the disadvantages of supplementation of culture media with FBS are manifold: (i) Serum is an ill-defined medium supplement, and thus an ambiguous factor in cell culture (Bjare, 1992;Gstraunthaler, 2003), (ii) serum batches display quantitative and qualitative variations in their composition and thus introduce a serious lot-to-lot variability (Price and Gregory, 1982), (iii) serum may contain different amounts of endotoxins, haemoglobin, and other adverse factors, and (iv) serum can be a potential source of microbial contaminants, such as fungi, bacteria, mycoplasma, viruses or prions (Dormont, 1999;Eliot, 1999;Wessman and Levings, 1999). thus, serum introduces several unknown variables into the tissue culture system (even et al, 2006;lindl und Gstraunthaler, 2008;Stoll and Spector, 1984).…”