Page 1401 - Veterinary Immunology, 10th Edition

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FIG. 42.3 Direct immunofluorescence of a smear of Clostridium
septicum. (See also Figs. 22.10 and 38.4.) (Courtesy Dr. J. Huff.)

Indirect Fluorescent Antibody Tests

Indirect fluorescent antibody tests can be used to measure
antibodies in serum or to identify specific antigens in tissues or cell
cultures. When measuring antibody levels, antigen is employed as a

tissue smear, section, or cell culture on a slide or coverslip. This is
incubated in serum suspected of containing antibodies to that
antigen. The serum is then washed off, leaving only specific
antibodies bound to the antigen (Fig. 42.4). These bound antibodies
may then be visualized by incubating the smear in FITC-labeled

antiglobulin. When the unbound labeled antiglobulin is removed
by washing and the slide examined, the presence of fluorescence
indicates that antibody was present in the test serum. The quantity

of antibody in the test serum may be estimated by testing
increasing dilutions of serum on different antigen preparations.

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