Final answer:
Indirect Immunofluorescent assay (IFA) is utilized for detecting autoantibodies, antibodies to tissue antigens, and antibodies to cellular antigens, making the correct answer 'D. All of the above'. It plays a crucial role in diagnosing autoimmune diseases and infections like syphilis.
Step-by-step explanation:
Indirect Immunofluorescent assay (IFA) is widely used for detection of autoantibodies, antibodies to tissue antigens, and antibodies to cellular antigens. It is an important tool in diagnosing autoimmune diseases by detecting antinuclear antibodies (ANA). The process involves fixing antigens to a surface, allowing patient serum to bind if corresponding antibodies are present, then adding a secondary antibody conjugated to a fluorogen to illuminate the antigen-antibody complexes.
For example, in the diagnosis of syphilis, an IFA test may use anti-treponemal antibodies from a patient's serum to bind to T. pallidum cells. After washing away unbound serum, a secondary antibody with a fluorogen is added. If fluorescence is observed, it indicates the presence of the bacteria bound by antibodies from the patient's serum.