What are the classes of antibodies?

Antibodies, also known as immunoglobulins (Igs), can be categorized into five main classes based on their structural and functional differences. Each class plays specific roles in the body's immune response. Here are the five classes of antibodies:

1. Immunoglobulin G (IgG):

- Most abundant class of antibodies

- Found in blood and other body fluids

- Can cross the placenta, providing protection to the fetus

- Involved in secondary immune responses and long-term immunity

- Activates the complement system, enhancing immune defenses

2. Immunoglobulin A (IgA):

- Found in saliva, tears, breast milk, and other mucosal secretions

- Protects mucosal surfaces from infections

- Can cross the placenta, but in lower amounts compared to IgG

- Plays a role in local immunity

3. Immunoglobulin M (IgM):

- First antibody produced in response to an infection

- Involved in primary immune responses

- Found in high concentrations in blood early during an infection

- Has a large molecular size and is efficient in activating the complement system

4. Immunoglobulin D (IgD):

- Found on the surface of B cells

- Acts as a receptor for antigens on B cells, triggering B cell activation and antibody production

- Involved in regulating immune responses

5. Immunoglobulin E (IgE):

- Found on the surface of mast cells and basophils

- Binds to allergens and triggers the release of histamine and other inflammatory mediators

- Involved in allergic reactions and anaphylaxis

Each antibody class has distinct properties and functions that enable the immune system to effectively recognize and respond to various pathogens and antigens.