Antibodies are formed by a complex process that involves specialized white blood cells called B cells. When a foreign substance, known as an antigen, enters the body, it triggers an immune response.
Here's how it works:
- Antigen Recognition: Antigen-presenting cells (APCs), like macrophages and dendritic cells, engulf and process the antigen. They then display fragments of the antigen on their surface using a molecule called MHC II.
- B Cell Activation: A B cell with a receptor that specifically binds to that antigen fragment encounters the APC. This interaction, along with signals from helper T cells, activates the B cell.
- Clonal Expansion: The activated B cell undergoes clonal expansion, rapidly dividing and creating many identical copies of itself.
- Differentiation: These clones differentiate into two types of cells:
- Plasma Cells: These cells produce and secrete large amounts of antibodies specific to the antigen.
- Memory B Cells: These cells remain in the body and "remember" the specific antigen. This allows for a faster and more robust immune response if the body encounters the same antigen again.
The antibodies produced by plasma cells circulate throughout the body and bind to the antigen, neutralizing it and marking it for destruction by other immune cells.
Examples:
- When you get a flu shot, the vaccine contains weakened or inactive flu virus antigens. This triggers your immune system to produce antibodies against these specific antigens.
- Allergic reactions are caused by the body's immune system overreacting to harmless substances like pollen or peanuts. This results in the production of antibodies that trigger the release of histamine and other inflammatory chemicals.
In summary, antibodies are formed by a complex and specific process that involves B cells, antigen-presenting cells, helper T cells, and the production of plasma cells.
