Final answer:
IgG subclasses differentiates in their structure and function, impacting their biological roles in immune responses. Variations like the ginglymus region and carbohydrate content affect their ability to activate complement, opsonization, cross the placenta, and bind to various immune system proteins.
Step-by-step explanation:
Differences Between IgG Subclasses
The differentiates between the subclasses of IgG antibodies lie in their structural and functional characteristics. Although all IgG antibodies consist of one variable domain and three constant domains within their heavy chains, the subclasses vary in their ginglymus regions and carbohydrate content. These variations affect their biological functions, such as half-life, ability to cross the placenta, and binding to certain types of cells and proteins, including the neonatal Fc receptor, Fc gamma receptors, and the complement component C1q. The IgG subclasses differ mainly in their ability to protect against pathogens and in their role in immune responses.
IgG1 and IgG3 are proficient at activating the complement system and opsonizing pathogens, aiding in their clearance. IgG2 is less effective at complement activation but is specialized for responses against polysaccharide antigens found on bacterial capsules. IgG4, in contrast, is associated with a lower capacity for complement activation and a higher tendency for anti-inflammatory responses, often found at elevated levels in the context of long-term antigen exposure, like chronic infections or allergies.