serum - watery fluid of the blood that resembles plasma but contains fibrinogenblood - the fluid (red in vertebrates) that is pumped by the heart; "blood carries oxygen and nutrients to the tissues and carries waste products away"; "the ancients believed that blood was the seat of the emotions" antiserum - blood serum containing antibodies against specific antigens; provides immunity to a disease serum albumin - albumin occurring in blood serum; serves to maintain the somatic pressure of the blood serum globulin - globulins occurring in blood serum and containing most of the antibodies of the blood opsonin - an antibody in blood serum that attaches to invading microorganisms and other antigens to make them more susceptible to the action of phagocytes milk whey, whey - the serum or watery part of milk that is separated from the curd in making cheese |