VMC 221: Veterinary Immunology and Serology (1+1)

DIRECT FLUORESCENT ANTIBODY TESTS (DIRECT FAT)

• This test is used to identify the presence of antigen.
• The antibody against a specific antigen (bacteria/virus) is first labeled with FITC.
• A tissue or smear containing the organism is fixed to a glass slide and incubated with FITC labeled antibody and washed to remove unbound antibody.
• When viewed under UV light, the organisms that bind the labeled antibody fluoresce brightly.
• This technique can detect low levels of organisms in samples.
• Example: used for detection of Rabies virus in cold acetone fixed brain impression smears, for detecting viruses growing in tissue culture or in tissues from infected animals, Mycobacterium paratuberculosis in faeces etc.