Neoantigens of the membrane attack complex of human complement

Area of Science:

• Immunology
• Complement system

Background:

• The membrane attack complex (MAC) is formed by five complement proteins (C5b-C9).
• MAC mediates complement-dependent cell membrane damage.
• MAC assembly occurs on target cell surfaces and in fluid phases.

Purpose of the Study:

• To investigate the antigenic properties of the MAC.
• To identify neoantigens formed during MAC assembly.

Main Methods:

• Production of antisera against the intact MAC.
• Adsorption of antisera with fresh human serum to achieve neoantigen specificity.
• Precipitation assays to detect MAC-specific antibodies.

Main Results:

• The soluble MAC showed reduced expression of precursor protein antigenic determinants.
• Antisera to the intact MAC contained antibodies to neoantigens absent in precursor proteins.
• Neoantigen-specific antibodies precipitated the MAC, indicating multiple neoantigenic sites.
• These antibodies reacted with both soluble and cell-bound MAC.

Conclusions:

• The MAC possesses unique neoantigens not present in its precursor proteins.
• These neoantigens are critical targets for MAC-specific antibodies.
• The findings confirm the structural integrity and antigenicity of the MAC in different states.