What type of test is used to measure the strength of antibodies in response to an antigen?

The titer test is specifically designed to measure the concentration of antibodies in a person’s serum in response to a particular antigen. This test quantifies how effectively the immune system responds to a pathogen or vaccine by identifying the highest dilution at which antibodies can still be detected, indicating the strength or level of the immune response.

In contrast, immunoblotting is primarily used to detect specific proteins in a sample and to confirm the presence of certain antibodies, but it does not provide a quantitative measure of antibody strength in response to an antigen. Flow cytometry is a technique used for analyzing the physical and chemical characteristics of cells or particles, which can include assessing the presence of specific markers but is not directly focused on measuring antibody titers. The serotonin test evaluates levels of serotonin in the body and is not related to measuring antibody strength. Thus, the titer test is the most appropriate and directly answers the question regarding the measurement of antibody strength in response to an antigen.