Which region determines whether an immunoglobulin molecule can fix complement?

Which region determines whether an immunoglobulin molecule can fix complement?

• A. VH
• B. CH
• C. VL
• D. CL

Answer: (B)

The ability of an immunoglobulin molecule to fix complement is primarily determined by the constant region of the heavy chain, referred to as the CH region. This region of the antibody structure is responsible for the effector functions of immunoglobulins, including complement activation. The CH region is composed of different isotypes of antibodies (IgM, IgG, etc.), and these isotypes possess distinct properties, including their ability to interact with the complement system. For instance, IgM and certain subclasses of IgG (like IgG1 and IgG3) are effective complement fixers because their CH regions have the appropriate structural characteristics to bind complement proteins effectively. In contrast, the variable regions (VH and VL) are primarily responsible for antigen binding and specificity, while the constant light chain region (CL) does not play a direct role in complement activation. Understanding the structure and function of these regions is critical in immunology, particularly regarding how antibodies mediate immune responses through complement fixation.

The ability of an immunoglobulin molecule to fix complement is primarily determined by the constant region of the heavy chain, referred to as the CH region. This region of the antibody structure is responsible for the effector functions of immunoglobulins, including complement activation.

The CH region is composed of different isotypes of antibodies (IgM, IgG, etc.), and these isotypes possess distinct properties, including their ability to interact with the complement system. For instance, IgM and certain subclasses of IgG (like IgG1 and IgG3) are effective complement fixers because their CH regions have the appropriate structural characteristics to bind complement proteins effectively.

In contrast, the variable regions (VH and VL) are primarily responsible for antigen binding and specificity, while the constant light chain region (CL) does not play a direct role in complement activation. Understanding the structure and function of these regions is critical in immunology, particularly regarding how antibodies mediate immune responses through complement fixation.