Regulation of humoral immunity by complement

Area of Science:

• Immunology
• Innate and adaptive immunity

Background:

• The complement system is crucial for innate immunity and regulates humoral immunity.
• Complement receptor CR2 (CD21) acts as a coreceptor on B cells during antigen activation.
• CR2 also retains antigens on follicular dendritic cells (FDCs), essential for B cell maturation.

Purpose of the Study:

• To review the role of complement in adaptive immunity.
• To focus on the interplay between CR2-associated antigens on B cells and CR2 on FDCs.
• To explore how CR2-ligand interactions influence B cell responses and autoimmunity.

Main Methods:

• Review of existing literature on complement system and B cell immunology.
• Analysis of the structural insights from the CR2-C3d cocrystal structure.
• Discussion of the implications for therapeutic strategies.

Main Results:

• CR2 on B cells facilitates antigen-induced activation.
• Antigen retention by CR2 on FDCs is critical for B cell clonal selection and affinity maturation.
• The CR2-C3d interaction regulates B cell antigen access and memory formation.

Conclusions:

• The complement system, particularly CR2, plays a vital role in bridging innate and adaptive immunity.
• Understanding CR2-mediated antigen display on FDCs is crucial for B cell memory.
• Targeting CR2 interactions offers potential for treating autoimmune disorders characterized by aberrant B cell activity.