Antibodies

Antibodies, also known as immunoglobulins, are proteins produced by the immune system in response to the presence of foreign substances called antigens. They play a crucial role in the body's defense against pathogens such as bacteria, viruses, and other harmful substances.

Structure of Antibodies

Antibodies have a Y-shaped structure composed of four polypeptide chains - two heavy chains and two light chains. Each antibody has a specific region that binds to a particular antigen, known as the antigen-binding site.

Functions of Antibodies

• Neutralization: Antibodies can neutralize toxins produced by bacteria and viruses, preventing them from harming the body.
• Opsonization: They can bind to pathogens, marking them for destruction by phagocytic cells such as macrophages.
• Agglutination: Antibodies can cause pathogens to clump together, making it easier for phagocytic cells to engulf and destroy them.
• Activation of the complement system: Antibodies can trigger the complement system, a group of proteins that work together to destroy pathogens.

Types of Antibodies

There are five main classes of antibodies, each with specific functions:

1. IgM: These are the first antibodies produced during an infection and are effective at agglutinating pathogens.
2. IgG: The most abundant antibodies in the blood and are involved in long-term immunity.
3. IgA: Found in mucous membranes, saliva, and tears, providing protection at body surfaces exposed to the external environment.
4. IgE: Associated with allergic reactions and defense against parasitic infections.
5. IgD: Found on the surface of B cells and involved in the activation of these cells.

Production of Antibodies

Antibodies are produced by B cells, a type of white blood cell. When a B cell encounters an antigen, it undergoes activation and differentiation into plasma cells, which are specialized to produce antibodies. Some B cells also become memory cells, providing long-term immunity against specific antigens.

Study Guide

Here are some key points to remember about antibodies:

• Understand the structure of antibodies, including the composition of heavy and light chains.
• Learn the functions of antibodies, such as neutralization, opsonization, and agglutination.
• Memorize the five classes of antibodies (IgM, IgG, IgA, IgE, IgD) and their respective roles in the immune system.
• Be familiar with the production of antibodies by B cells and the formation of memory cells for long-term immunity.