Azide Free Serum for cell culture FBS fetal bovine serum. Filtered serum for sterility. The polyclonal serum contains no red or white blood cells or clotting factors; it is the blood plasma not including the fibrinogens. Serum includes all proteins and antibodies not used in blood clotting (coagulation) and all the electrolytes, antibodies, antigens, hormones, and any exogenous substances like drugs and microorganisms. Plasmas on request.