In blood, the serum is the component that is neither a blood cell (serum does not contain white or red blood cells) nor a clotting factor, it is the blood plasma with the fibrinogens removed. Serum includes all proteins not used in blood clotting and all the electrolytes, antibodies, antigens, hormones, and any exogenous substances (e.g., drugs and microorganisms). Description: Normal Cat Serum was obtained from healthy donors of US origin. Synonyms: Normal Cat Serum.