Antibodies as natural adjuvants

Area of Science:

• Immunology
• Molecular Biology

Background:

• Antibodies binding to antigens can profoundly influence the resulting immune response.
• This modulation can lead to significant suppression (>99%) or enhancement (>100-fold) depending on antibody class and antigen type.

Purpose of the Study:

• To elucidate the diverse mechanisms by which different antibody classes modulate immune responses.
• To differentiate between antibody-mediated enhancement and suppression of immune reactions.

Main Methods:

• The study reviews existing literature and experimental data on antibody-antigen interactions.
• Mechanisms were analyzed based on antibody subclasses (IgM, IgG1, IgG2a, IgG2b, IgE) and their interactions with cellular receptors (Fcγ-receptors, CD23) and the complement system.

Main Results:

• Immunoglobulin M (IgM) and Immunoglobulin G3 (IgG3) enhance responses via the complement system, likely by increasing antigen concentration on follicular dendritic cells.
• Immunoglobulin G1 (IgG1), IgG2a, IgG2b, and Immunoglobulin E (IgE) enhance responses to protein antigens by activating Fcγ-receptors or CD23, potentially increasing antigen presentation to T helper cells.
• IgG antibodies of all subclasses can suppress responses to particulate antigens like erythrocytes, a mechanism utilized clinically to prevent RhD immunization.

Conclusions:

• Antibody-mediated immune response modulation is complex, with distinct mechanisms for enhancement and suppression.
• Different antibody classes and subclasses play specific roles in regulating immune reactions through receptor-mediated pathways and antigen presentation.
• Understanding these mechanisms has implications for both basic immunology and clinical applications, such as preventing hemolytic disease of the newborn.