Fab antigen-binding sites

Definition

Fab antigen-binding sites are regions on an antibody that bind to antigens with high specificity. These sites are located on the variable regions of the antibody's light and heavy chains.

5 Must Know Facts For Your Next Test

1. Fab stands for 'Fragment, antigen-binding' and is crucial for the antibody's ability to recognize and bind specific antigens.
2. Each Fab fragment consists of one constant and one variable domain from both the heavy and light chains of the antibody.
3. The binding specificity is determined by the unique amino acid sequences in these variable regions, allowing antibodies to target a vast array of antigens.
4. Enzymatic cleavage by papain can separate an antibody into two Fab fragments and one Fc fragment, which facilitates study of their functions separately.
5. Fab fragments can be used therapeutically to block specific interactions between pathogens and host cells without triggering immune effector functions.

Review Questions

• What does 'Fab' stand for in the context of antibodies?
• How do Fab antigen-binding sites contribute to an immune response?
• What enzyme is commonly used to cleave antibodies into Fab fragments?

Related terms

Antibody: A protein produced by B cells that binds specifically to antigens.

Antigen: Any substance that induces an immune response, typically recognized by antibodies or T-cell receptors.

Fc Fragment: The constant region of an antibody molecule that interacts with cell surface receptors and complement proteins.