Monoclonal antibodies against the complement control protein factor H (beta 1 H)

Area of Science:

• Immunology
• Complement System Biology

Background:

• Factor H is a crucial regulator of the human complement system.
• Understanding Factor H's interactions with complement components is vital for immune research.

Purpose of the Study:

• To characterize two novel monoclonal antibodies against human Factor H.
• To investigate the distinct binding and functional activities of Factor H with soluble and surface-bound C3b.
• To utilize these antibodies for immunoprecipitation and quantification of Factor H.

Main Methods:

• Production and characterization of mouse monoclonal antibodies (IgG subclass) against human Factor H.
• Assays to measure Factor H cofactor activity in Factor I-mediated C3b cleavage.
• Inhibition assays to study Factor H binding to surface-bound C3b (EAC3b).
• Indirect immunoprecipitation to detect Factor H in various primate and animal sera.
• Radioimmunoassay for quantifying Factor H concentration in human plasma.

Main Results:

• One antibody (MRC OX 24) enhances Factor H cofactor activity, while the other (MRC OX 23) modulates this effect.
• MRC OX 24 inhibits Factor H binding to surface-bound C3b, an effect reduced by MRC OX 23.
• Factor H interactions differ between soluble C3b and surface-bound C3b.
• Factor H was specifically precipitated from human and other primate sera, but not from other species.
• Factor H concentration in human plasma was determined using radioimmunoassay.

Conclusions:

• The study elucidates distinct mechanisms of Factor H interaction with soluble versus surface-bound C3b.
• The developed monoclonal antibodies are specific reagents for studying complement regulation and Factor H.
• These antibodies facilitate the detection and quantification of Factor H across different species and in human plasma.