Antigenicity of Bovine Milk Xanthine Oxidase in Guinea Pigs

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Abstract
Six female and 4 male albino guinea pigs were immunized with active purified xanthine oxidase of bovine milk mixed with equal volume of Freund''s complete adjuvant. One male and 1 female were immunized with heat-inactivated xanthine oxidase mixed with equal volume of adjuvant. Two males and 4 females were controls and received a phosphate buffer mixed with equal volume of adjuvant. The mixtures were administered intradermally and s.c. at weekly intervals for 6 consecutive wk, with blood samples collected weekly. The enzyme was antigenic as determined by the coated tanned [sheep] red blood cell method. After the 3rd weekly immunization, precipitating antibodies were in the sera of animals that received the active enzyme. Hemagglutination titers increased during subsequent weeks, and reached a maximum after the 6th weekly immunization. Antisera from animals immunized with heat-inactivated xanthine oxidase gave a positive response similar to that with animals immunized with the active enzyme. When the same antisera were tested with sheep red blood cells coated with heat-inactivated enzyme, no hemagglutination was observed. Ouchterlony double gel-diffusion tests showed that it may be possible to differentiate between antibodies elicited to active and heat-inactivated xanthine oxidase. [The possible relationship of xanthine oxidase to atherosclerosis is discussed.].