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🦠microbiology review

Antibody Titer

Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025

Definition

An antibody titer is a measurement of the concentration or amount of antibodies present in a person's blood. It is a quantitative assessment of the body's immune response to a specific antigen, providing information about the level of antibodies produced.

5 Must Know Facts For Your Next Test

  1. Antibody titer is a measure of the concentration or amount of a specific antibody present in a person's blood, indicating the strength of the immune response.
  2. High antibody titers suggest a strong immune response, while low titers may indicate a weaker or waning immune response.
  3. Antibody titers are commonly used to assess the effectiveness of vaccines, monitor the progression of infectious diseases, and diagnose autoimmune disorders.
  4. Agglutination assays, such as the hemagglutination inhibition (HAI) test, utilize the ability of antibodies to cause the clumping of target cells or particles to measure antibody titers.
  5. Detecting antigen-antibody complexes through techniques like enzyme-linked immunosorbent assay (ELISA) can also be used to determine antibody titers and evaluate the immune response.

Review Questions

  • Explain how antibody titers are used to assess the effectiveness of vaccines.
    • Antibody titers are commonly used to evaluate the immune response and effectiveness of vaccines. After receiving a vaccine, the body produces specific antibodies to the vaccine antigen. By measuring the antibody titer, healthcare providers can determine the level of antibodies present, which indicates the strength of the immune response. Higher antibody titers suggest a more robust immune response and greater protection against the targeted disease, while lower titers may indicate the need for a booster dose or revaccination.
  • Describe how agglutination assays, such as the hemagglutination inhibition (HAI) test, are used to measure antibody titers.
    • Agglutination assays, like the HAI test, utilize the ability of antibodies to cause the clumping or agglutination of target cells or particles. In the HAI test, the target cells are typically red blood cells (RBCs) that have been coated with a viral antigen. When antibodies specific to that antigen are present in a sample, they will bind to the RBCs and cause them to agglutinate. By serially diluting the sample and determining the highest dilution that still causes agglutination, the test can quantify the antibody titer, providing a measure of the immune response to the targeted virus or pathogen.
  • Analyze how the detection of antigen-antibody complexes, such as through enzyme-linked immunosorbent assay (ELISA), can be used to determine antibody titers and evaluate the immune response.
    • The detection of antigen-antibody complexes, as in the ELISA technique, is another method for determining antibody titers and assessing the immune response. In ELISA, the target antigen is immobilized on a solid surface, and the sample containing antibodies is added. If the antibodies are present, they will bind to the antigen, forming antigen-antibody complexes. These complexes can then be detected and quantified using enzyme-labeled secondary antibodies that bind to the primary antibodies. By measuring the intensity of the enzyme-mediated signal, the ELISA can provide a quantitative measure of the antibody titer, reflecting the level of the immune response to the target antigen. This information is valuable for monitoring the effectiveness of vaccines, diagnosing infections, and evaluating autoimmune disorders.