Page 1435 - Veterinary Immunology, 10th Edition

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FIG. 42.29 The principle of the complement fixation test.
Complement, if fixed by antigen and antibody, is unavailable to lyse
the target cells in the indicator system. In the absence of antibody,
the complement remains unfixed and is available to lyse the
indicator system. (Modified from Roitt I: Essential immunology, Oxford, 1971,
Blackwell Science.)

Cytotoxicity Tests

Complement may cause membrane damage, not only to
erythrocytes but also to nucleated cells and to protozoa. Antibodies
against cell surface antigens thus may be measured by reacting
target cells with antibody and complement and estimating the

resulting cell death. This form of assay has been employed to type
cells by determining which major histocompatibility complex
(MHC) class I molecules they are expressing.

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