The technique shown in the image uses what type of antibody?

• A. Fluorescent ragged antibody
• B. Enzyme-labeled antibody
• C. Radioactive antibody
• D. Unlabeled antibody

Answer: (A)

The technique relies on an antibody that is conjugated to a fluorescent dye, enabling visualization under a fluorescence microscope. When the labeled antibody binds its target, the fluorophore emits light at a specific wavelength after excitation, highlighting the location of the antigen in the sample. This is immunofluorescence, where the signal comes from the fluorescent tag on the antibody itself, allowing direct (or indirect, if a labeled secondary is used) visualization of the target.

This differs from enzyme-labeled antibodies, which produce a color change via a chromogenic substrate; radioactive antibodies, which require autoradiography to detect radioactivity; and unlabeled antibodies, which need another labeled reagent to reveal binding. The fluorescent signal shown in the image specifically points to a fluorescently labeled antibody as the detecting method.