Figure 4.17.

An antigen capture, lateral flow immunoassay. The test strip contains three key assay reagents. In this example a gold-conjugated antibody binds to virus in the test sample. The liquid moves across the slide by capillary action to the Test (T) strip. The T strip contains membrane bound antiviral antibody. It will bind to capture the virus particles and their associated gold tagged antibodies to generate a visible signal at the T strip. If no virus is present in the sample, the gold-labeled antibody travels past the T strip and binds to anti-immunoglobulin antibodies bound at the C strip. A positive sample must show color reactions at both the T strip and the C strip. A negative sample must show a color reaction at the C strip (to validate that the test worked correctly).