The five classes (isotypes) of human antibodies are IgM, IgD, IgG, IgA, and IgE. These antibodies are distinguished by their heavy (H) chains, each contributing to distinct characteristics and roles in the immune system.
Antibody Isotypes
Here's a breakdown of each antibody isotype:
| Isotype | Description |
|---|---|
| IgM | Often the first antibody produced during an immune response. |
| IgD | Primarily found on mature B cells; function not entirely understood. |
| IgG | The most abundant antibody in blood plasma, making up 70-75% of human antibodies. |
| IgA | Found in mucosal areas, preventing pathogens from colonizing. |
| IgE | Plays a role in allergic reactions and immunity against parasites. |
Understanding Antibody Diversity
The different classes of antibodies ensure a broad range of immune responses and specificity. Each class targets different threats, ensuring thorough protection against antigens.
- IgG is the most common antibody in the blood, providing long-term immunity.
- IgM is produced initially during infection and then gives way to IgG.
- IgA is found in secretions such as breast milk, tears, and saliva.
- IgE triggers allergic reactions by interacting with mast cells and basophils.
- IgD is not well understood but is known to help B cells mature.
These five isotypes of antibodies each play important and distinct roles in immune function.
