The addition of a carrier to cytokine solutions can increase the stability and shelf-life of the protein. Recombinant Human HSA has ultra-low endotoxin levels and is ideal for use as a carrier protein. The use of bovine serum albumin is quite common for this purpose, but has the disadvantage of being of animal origin and quite frequently increases the endotoxin level of the resulting solution. HumanZyme has introduced recombinant Human Albumin expressed in engineered human cells cultured in serum-free chemically defined media.