SPAC22F8.04 Antibody

Antibody Structure and Function

Antibodies (immunoglobulins) are Y-shaped glycoproteins composed of two heavy chains and two light chains, with distinct constant (Fc) and variable (Fab) regions . The Fc region interacts with effector molecules (e.g., Fc receptors on immune cells) to mediate functions like phagocytosis or complement activation .

Antigen Cross-Presentation and DC Function

Dendritic cells (DCs) rely on Sec22b-dependent cross-presentation to activate CD8+ T cells against tumor antigens . Impaired Sec22b expression in DCs leads to reduced antitumor immunity and resistance to anti-PD-1 therapy . This mechanism underscores the importance of Fc-mediated interactions in immunotherapy:

• Sec22b Role: Traffics antigens from phagosomes to the endoplasmic reticulum for cross-presentation .

• Therapeutic Implications: Enhancing DC cross-presentation could improve checkpoint inhibitor efficacy .

IgG Purification and Functional Integrity

Low-pH purification methods (e.g., Protein G) can induce IgG aggregation, altering Fc receptor binding and effector functions . For example:

• Protein G vs. Melon Gel: Protein G-purified IgG exhibits higher FcγRIIIa binding and phagocytosis activity due to aggregates .

• Impact on Therapy: Aggregated IgG may enhance antibody-dependent cellular phagocytosis (ADCP) but risks off-target effects .

IgG Subclass-Specific Properties

IgG subclasses (IgG1–IgG4) exhibit distinct biological activities :

Antibody Glycosylation

Glycosylation at the Fc region modulates effector functions . For example:

• Afucosylated IgG1: Enhances ADCP via increased FcγRIIIa binding .

• High-mannose glycans: Promote complement activation .