The IgG subclasses differ mainly in

The IgG subclasses differ mainly in

• A. the type of L chain.
• B. the arrangement of disulfide bonds.
• C. the ability to act as opsonins.
• D. molecular weight.

Answer: (B)

IgG subclass differences come from the heavy chain region, especially how the two heavy chains are connected by disulfide bonds in the hinge area. The pattern and number of these disulfide bonds alter hinge length and how the Fc portion is oriented, which changes how the antibody interacts with Fc receptors on phagocytes and with the C1q component of complement. Those structural differences, driven by the disulfide bond arrangement, are what set the subclasses apart functionally and structurally. Light-chain type is not what defines a subclass, and molecular weight is not the main distinguishing feature.

IgG subclass differences come from the heavy chain region, especially how the two heavy chains are connected by disulfide bonds in the hinge area. The pattern and number of these disulfide bonds alter hinge length and how the Fc portion is oriented, which changes how the antibody interacts with Fc receptors on phagocytes and with the C1q component of complement. Those structural differences, driven by the disulfide bond arrangement, are what set the subclasses apart functionally and structurally. Light-chain type is not what defines a subclass, and molecular weight is not the main distinguishing feature.