What is an Antibody?

An antibody, or immunoglobulin (Ig), is a Y-shaped protein made by B cells of the immune system. Its main job is to identify and neutralize antigens — foreign substances such as viruses, bacteria, fungi, and toxins.

🔬 Structure of Antibodies

• Consist of four polypeptide chains:

  • 2 heavy chains

  • 2 light chains

• Shaped like a Y

• Variable region (arms): specifically binds to a unique antigen

• Constant region (stem): determines the antibody class and function

Each antibody binds to only one specific antigen, like a lock and key.

🛡️ Functions of Antibodies

1. Neutralization – Block harmful effects of pathogens or toxins

2. Opsonization – Tag pathogens for destruction by immune cells

3. Agglutination – Clump pathogens together for easier removal

4. Complement activation – Trigger destruction via the complement system

5. ADCC (Antibody-dependent cellular cytotoxicity) – Direct immune cells to kill infected or cancerous cells

🧪 Types (Classes) of Antibodies

🧬 How Antibodies Are Made

1. Pathogen enters body

2. B cells detect antigen

3. Activated B cells transform into plasma cells

4. Plasma cells produce and release antibodies

5. Some B cells become memory cells for future immunity

📜 History & Discovery of Antibodies

1. 1890 – First Discovery of Antitoxins (early antibodies)

• Emil von Behring & Shibasaburo Kitasato

• Found that serum from animals infected with diphtheria or tetanus could neutralize the toxins in other animals

• Called these substances "antitoxins"

• 🏆 Nobel Prize in Medicine (1901) – von Behring (first ever Nobel in medicine)

2. 1900 – Ehrlich’s Side Chain Theory

• Paul Ehrlich proposed that immune cells have side chains (receptors) that bind to antigens

• First theoretical explanation of antibody specificity

3. 1901 – Karl Landsteiner Discovers Blood Groups

• Showed that antibodies cause agglutination of incompatible red blood cells

• Basis of blood typing (ABO)

4. 1959 – Structure Discovered

• Rodney Porter and Gerald Edelman independently discovered the Y-shaped structure of antibodies

• 🏆 Nobel Prize (1972)

5. 1975 – Monoclonal Antibodies Invented

• Georges Köhler and César Milstein developed the hybridoma technique to produce identical (monoclonal) antibodies in the lab

• 🏆 Nobel Prize (1984)

💊 Medical Uses of Antibodies

1. Vaccines – stimulate production of natural antibodies

2. Monoclonal antibody drugs:

   • Cancer treatment (e.g., trastuzumab for breast cancer)

   • Autoimmune diseases (e.g., adalimumab for arthritis)

   • Infectious diseases (e.g., COVID-19 antibody therapies)

3. Diagnostic tools:

   • Rapid tests (e.g., COVID-19, pregnancy tests)

   • Laboratory diagnostics (e.g., ELISA)

🌍 Global Impact

• Antibodies are essential to immunity

• Foundational in modern medicine, biotechnology, and vaccine development

• Antibody technology helps in organ transplants, allergy testing, cancer therapies, and infectious disease control

🧠 Fun Facts

• Humans can make over 1 billion unique antibodies

• IgG is the only antibody that crosses the placenta to protect the fetus

• Llamas produce a special type of nanobody used in cutting-edge research