Characteristics of Direct and Indirect Complement-Fixing Antibodies Obtained from Turkeys Infected with Ornithosis Agent

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Abstract
Summary: The antibody response of turkeys experimentally infected with ornithosis was measured by three different methods: indirect complement-fixation (ICF), direct complement-fixation utilizing a detergent-extracted soluble antigen (DCF-det), and a DCF method in which a small amount of fresh normal fowl serum was added (DCF-Brum). Possible explanations for the discrepancies between the titers obtained by these three assay methods were tested by studying the physical properties of the antibodies. Early acute-phase antisera (9–14 days) contained 7 S γ2 antibody, as determined by all three tests. These early antisera also contained anti-ornithosis activity detectable only by ICF, which sedimented in sucrose gradients intermediate between the 7 S and 19 S fractions. The ICF antibody migrated electrophoretically in the γ1- and γ2-globulin regions. Primary anti-BSA turkey sera contained three distinct populations of hemagglutinins (HA): 19 S γ1, 19 S γ2 and 7 S γ2. In contrast, only 7S anti-BSA antibodies were detected in primary antisera by an antigen-binding technique. The chromatographic properties of 7 S anti-ornithosis antibody and 7 S anti-BSA HA differed; the anti-ornithosis antibodies were eluted with a lower salt concentration than were the more strongly anionic-binding 7 S anti-BSA HA. Reasons for the absence of 19 S anti-ornithosis antibody are discussed.

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