Three rat monoclonal antibodies to human C3

Area of Science:

• Immunology
• Biochemistry

Background:

• The complement system, particularly complement component 3 (C3), plays a crucial role in innate and adaptive immunity.
• Monoclonal antibodies are valuable tools for dissecting protein structure and function, including complement proteins.

Purpose of the Study:

• To generate and characterize monoclonal antibodies against human C3.
• To investigate the antigenic determinants recognized by these antibodies and their potential impact on C3 function.

Main Methods:

• Hybridoma technology was employed, fusing rat myeloma cells with spleen cells from C3-immunized rats.
• Agglutination analysis and co-precipitation assays were used to determine antibody specificities.
• Functional inhibition assays were performed to assess the impact on C3 activity.

Main Results:

• Three monoclonal antibodies (clones 4, 3, and 9) were successfully generated against human C3.
• Clone 4 recognized the C antigen in C3c. Clones 3 and 9 exhibited unusual reactivity patterns with C3d and C3bi, respectively.
• Anomalous co-precipitation results were observed, suggesting complex epitope interactions or potential internal sequence duplications within C3.
• None of the antibodies significantly inhibited C3 functions.

Conclusions:

• The generated monoclonal antibodies provide novel tools for C3 research, with clone 4 offering specific recognition of the C antigen.
• The unusual properties and specificities of clones 3 and 9 highlight the complexity of C3 antigenicity and necessitate further investigation.
• These antibodies, despite not inhibiting C3 function, offer unique insights into C3 structure and antigen-antibody interactions.