An example of a naturally occurring anti-cE (Rh27) that binds complement

Area of Science:

• Immunology
• Transfusion Medicine
• Serology

Background:

• Rh27 is a high-frequency antigen in Rh blood group system.
• Naturally occurring antibodies against Rh antigens are rare, especially those that bind complement.

Purpose of the Study:

• To characterize a novel naturally occurring antibody with anti-Rh27 specificity.
• To investigate the immunoglobulin class and complement-binding properties of this antibody.

Main Methods:

• Serum absorption studies using R1R1 and RZR1 cells.
• Treatment with reducing agents to assess antibody class.
• Indirect antiglobulin tests with monospecific reagents (anti-IgM, anti-IgA, anti-IgG, anti-C3, anti-C4).

Main Results:

• Absorption studies confirmed anti-Rh27 specificity.
• Antibody activity was lost after reduction, indicating predominantly IgM.
• The antibody showed weak reactions with anti-IgM and anti-IgA, no reaction with anti-IgG.
• Strong complement activation was observed with anti-C3 and anti-C4 reagents.

Conclusions:

• This is the first reported case of a naturally occurring, complement-binding anti-Rh27 antibody.
• The antibody is predominantly IgM and activates both classical and alternative complement pathways.
• This finding has implications for understanding Rh alloimmunization and transfusion reactions.