Virus and its Antibody are Brought Together in Several Ways
i) Precipitation test: In this antibodies and antigens are mixed together in solution.
ii) Ring interface test: They meet at the interface between 2 solutions containing each separately.
iii) Gel diffusion test: The diffuse towards each other through an agar gel and meet in a zone in suitable concentration.
iv) Agglutination reaction: Sometimes antigen is observed on a surface of large particles, such as a cell, plastid and these are precipitated by addition of antibodies.