Complement inhibitor of rat cell membrane resembling mouse Crry/p65

Area of Science:

• Immunology
• Complement System Biology
• Erythrocyte Research

Background:

• Neuraminidase-treated rat erythrocytes resist homologous complement-mediated lysis via the alternative pathway.
• Heterologous serum complement can readily lyse these treated erythrocytes.
• A need exists to understand homologous complement regulation on rat erythrocytes.

Purpose of the Study:

• To identify a factor enabling homologous complement-mediated lysis of neuraminidase-treated rat erythrocytes.
• To characterize the target antigen of the developed monoclonal antibody.
• To investigate the potential role of the identified antigen in complement regulation.

Main Methods:

• Development of a monoclonal antibody (mAb512) specific for rat erythrocyte membrane components.
• Hemolysis assays using neuraminidase-treated rat erythrocytes and homologous rat serum.
• Western blotting to detect target protein molecular masses.
• C3b deposition assays on rat myeloma cells.
• Immunosorbent purification and partial peptide sequencing of the target antigen (512Ag).

Main Results:

• mAb512 induced homologous complement-mediated lysis of neuraminidase-treated rat erythrocytes.
• mAb512 detected 65 kDa and 55 kDa membrane proteins on rat erythrocytes.
• mAb512 treatment led to C3b deposition on rat myeloma cells in the presence of rat serum.
• Purified 512Ag showed significant homology to mouse Crry/p65 upon partial sequencing.

Conclusions:

• mAb512 is a valuable tool for studying homologous complement activation on rat erythrocytes.
• The identified 512Ag is likely the rat homolog of mouse Crry/p65, a complement regulator.
• This finding provides insights into the molecular mechanisms of complement regulation in rats.