What procedure is described when a substrate is exposed to patient serum, washed, and then anti-human immunoglobulin labeled with a fluorochrome is added?

The described procedure refers to the indirect fluorescence method, which is a common immunological technique used to detect the presence of specific antibodies in patient serum. In this procedure, a substrate (such as a slide or microtiter plate) is coated with an antigen that can bind to the antibodies present in the patient's serum. Following this, the serum is applied to the substrate, allowing any antibodies specific to the antigen to bind.

After allowing sufficient time for binding, the substrate is washed to remove any unbound serum components. The next step involves adding a secondary antibody, which is anti-human immunoglobulin labeled with a fluorochrome. This secondary antibody specifically binds to the human antibodies that are attached to the substrate.

The labeling with a fluorochrome allows for visualization under a fluorescence microscope. The presence of binding indicates that specific antibodies were present in the patient's serum, confirming an immune response to the antigen.

This method contrasts with direct fluorescence, where the primary antibody itself is labeled with a fluorochrome and applied directly to the sample. It is also distinct from competitive enzyme immunoassays, which function differently by measuring the intensity of signal that inversely correlates with the amount of antigen present. Lastly, the Western blot method involves separating proteins by