The role of complement and IgG on zymosan opsonization

Area of Science:

• Immunology
• Complement System
• Cellular Immunology

Background:

• Zymosan particle interaction with granulocytes requires opsonization for effective respiratory burst activation.
• Understanding the specific serum factors involved in zymosan opsonization is critical for elucidating immune response mechanisms.

Purpose of the Study:

• To investigate the essential serum factors, including immunoglobulins (Ig) and complement pathways, required for zymosan opsonization.
• To determine the distinct roles of the classical complement pathway (CCP) and alternative complement pathway (ACP) in this process.

Main Methods:

• Utilized granulocyte chemiluminescence assays to measure opsonization efficiency.
• Employed hypogammaglobulinemic serum (HGS) deficient in Ig, and manipulated complement pathways (ACP, CCP) through heat inactivation and chemical treatments (EGTA, MgCl2).

Main Results:

• Hypogammaglobulinemic serum (HGS) showed significantly reduced opsonic activity (66% of normal serum), highlighting the role of Ig.
• IgG restored opsonic activity in HGS, but heat-inactivated serum or isolated IgG alone lacked activity.
• Inactivation of the alternative complement pathway (ACP) abolished normal serum activity, indicating its essentiality.
• Selective inactivation of the classical complement pathway (CCP) reduced opsonic activity by 26%, suggesting its participation.

Conclusions:

• The alternative complement pathway (ACP) is essential for zymosan opsonization.
• Both the classical complement pathway (CCP) and immunoglobulins (IgG) also play significant, participatory roles in zymosan opsonization.
• Optimal zymosan opsonization is a multi-factorial process involving the ACP, CCP, and IgG.