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Deficiency of C1r in human serum. Effects on the structure and function of macromolecular C1

R J Pickering, G B Naff, R M Stroud

    The Journal of Experimental Medicine
    |April 1, 1970
    PubMed

    Insights

    This study reveals that a deficiency in complement component 1r (C1r) function causes low hemolytic complement activity. This C1r defect impairs the assembly of the C1 complex, crucial for immune response.

    Area of Science:

    • Immunology
    • Complement System Biology

    Background:

    • The complement system is vital for innate immunity.
    • Complement component 1 (C1) is the initial activator of the classical complement pathway.
    • Deficiencies in C1 can lead to impaired immune responses.

    Purpose of the Study:

    • To investigate the cause of hemolytic complement deficiency in human serum.
    • To elucidate the specific roles of C1 subcomponents (C1q, C1r, C1s) in C1 assembly and function.

    Main Methods:

    • Analysis of human serum with markedly deficient hemolytic complement activity.
    • Assays to determine the concentration and function of C1q, C1r, and C1s proteins.

    Main Results:

    • The hemolytic deficiency was attributed to a selective lack of hemolytic C1 activity.
    • A profound deficit in C1r function was identified, with normal C1q and reduced C1s protein and function.
    • Normal C1q concentration and function, despite C1r deficit, suggest distinct cellular origins for C1q and C1r.

    Conclusions:

    • C1r plays a critical role in the assembly and stability of the macromolecular C1 complex.
    • The findings suggest that C1r is essential for proper C1q-C1s association, even in the presence of calcium.
    • Distinct synthesis pathways for C1q and C1r are implied by their independent expression levels.

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