Plasma is in everyone. Plasma is the colorless liquid part of blood in which the blood cells viz. RBCs, WBCs, Platelets and other cellular components etc. float. It is single largest component of the blood. It comprises 55% of the blood in body. And it contains water , salts, enzymes, antibody and other proteins. Different constituents of Plasma perform different important functions in the body. Antigens are molecules capable of stimulating an immune response. Antibodies are proteins produced by immune system. Antibodies help to fight the disease.