What are the advantages and disadvantages of direct method, indirect method and complement binding fluorescence immunoassay for fluorescent antibody staining?

(1) Direct method: ① Advantages: simple operation, strong specificity and few nonspecific fluorescence interference factors; Disadvantages: the sensitivity is low, so it is necessary to prepare specific fluorescent antibodies for each antigen.

(2) Indirect method: ① Advantages: The sensitivity is higher than that of direct method, and a fluorescent antibody can be used to detect various antigens or antibodies; Disadvantages: there are many factors involved, which are prone to nonspecific fluorescence and long operation time.

(3) Complement binding method: ① Advantages: High sensitivity. Fluorescent antibody can detect all kinds of antigens or antibodies, which is suitable for antigen-antibody system of any animal. Disadvantages: Non-specific fluorescent staining is easy to occur, and fresh complement is needed for each test, so the operation is complicated.