Summary
Y-shaped proteins made by B cells that bind specific antigens and mark them for destruction.
In depth
Structure: two heavy and two light chains with variable regions that bind antigen and a constant region (Fc) that signals to immune cells. Functions: neutralisation, opsonisation, agglutination and complement activation.
Antigen binding uses six loops (CDRs) in the variable regions. Affinity is increased by hypermutation. Antibodies can cross-link antigens, leading to agglutination or precipitation.
Key idea: antibodies tag, neutralise and recruit other defences.
Each antibody binds an antigen at the tips of the Y (Fab) with two identical binding sites, and the Fc region interacts with receptors and complement. Functions include neutralisation (blocking viruses and toxins), opsonisation (tagging for phagocytosis), complement activation, agglutination and antibody-dependent cell killing by NK cells. Affinity maturation increases binding strength by somatic hypermutation in germinal centres.
Antibodies are measured by ELISA, which underlies tests for pregnancy hormones and infections. Therapeutic antibodies treat cancer, autoimmunity and infections. Emil von Behring received the first Nobel Prize in Medicine (1901) for antitoxin (antibody) therapy against diphtheria.
Common mistake: the immune system does not make antibodies in response to a need; B cells carrying matching receptors are selected from a pre-existing set.
Frequently asked questions
What is Antibodies?
Y-shaped proteins made by B cells that bind specific antigens and mark them for destruction.
Which area of biology covers Antibodies, and how advanced is it?
Antibodies is one of the 52 topics in Immunology & Disease. It is rated Beginner, so it suits learners who are starting out in biology. Related topics in this area include B Lymphocytes, Antibody Classes, Antibody Diversity.
Can you give an example of Antibodies?
Antibodies against the tetanus toxin neutralise it.
What should I learn before Antibodies?
Antibodies is a Beginner topic, so no earlier topic is required. Other Beginner topics in Immunology & Disease that pair well with it include Immune System, Viruses, Innate Immunity.
What topics are related to Antibodies?
The closest topics to Antibodies are B Lymphocytes, Antibody Classes, Antibody Diversity, Adaptive Immunity. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Antibodies?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Antibodies. To practise the whole of Immunology & Disease, use the Immunology & Disease quiz.
How is Antibodies different from B Lymphocytes?
Antibodies: Y-shaped proteins made by B cells that bind specific antigens and mark them for destruction. B Lymphocytes: Cells that mature into plasma cells producing antibodies and into memory B cells. Read both side by side and note what each one explains.
What is a common mistake about Antibodies?
The immune system does not make antibodies in response to a need; B cells carrying matching receptors are selected from a pre-existing set.
How should I study Antibodies step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with B Lymphocytes and explain the difference aloud. Finally, take the Immunology & Disease quiz and come back to this page for any question you miss.