Dec 9, 2008 · We found that Lys (A200) and Lys (C170) are significant for binding with both immunoglobulins. In addition, two C1q-specific scFv antibodies known as potent inhibitors of C1q-IgG and -IgM interactions were used in the epitope mapping analysis.

May 30, 2019 · Based on the structural data, we hypothesize a C1q-transmitted surface trigger that activates C1, leading to C4 cleavage and C4b deposition on membranes. Antigen binding by serum Ig-M (IgM) protects against microbial infections and helps to prevent autoimmunity, but causes life-threatening diseases when mistargeted.

The data indicate the structural arrangement of pentameric and hexameric IgM upon antigen binding, exposing the C1q-binding sites with both adopting hexagonal symmetry. The structures reveal the entire C1qr 2 s 2 complex and elucidate several protein–protein interactions with …

Nov 12, 2008 · We found that Lys A200 and Lys C170 are significant for binding with both immunoglobulins. In addition, two C1q-specific scFv antibodies known as potent inhibitors of C1q−IgG and −IgM interactions were used in the epitope mapping analysis.

The complement component 1q (or simply C1q) is a protein complex involved in the complement system, which is part of the innate immune system. C1q together with C1r and C1s form the C1 complex. Antibodies of the adaptive immune system can bind antigen, forming an antigen-antibody complex.

Jan 19, 2017 · The classical pathway of complement is activated upon binding of the 774-kDa C1 complex, consisting of the recognition molecule C1q and the tetrameric protease complex C1r 2 s 2, to a variety of activators presenting specific molecular patterns such as IgG- and IgM-containing immune complexes.

Jul 1, 2005 · C1q is the recognition component of the classical pathway. The best-known ligands for C1q are the Fc regions of aggregated immunoglobulin (Ig)G and IgM molecules in immune complexes. Such binding triggers activation of the classical pathway.

After recognizing IgG- and IgM-containing immune complexes, C1q, in association with C1r and C1s complexes that yields C1 molecule, triggers the classical pathway activation. However, C1q is not always dependent on the binding of IgG or IgM to target ligands, primarily pathogens, in order to perform its duty as a potent innate immune molecule.

Sep 2, 2021 · Fusion of the C-terminal tailpiece of IgM promoted spontaneous hIgG hexamer formation, resulting in enhanced C1q recruitment and complement-dependent cytotoxicity (CDC) but with off-target...

May 17, 2024 · Hexameric IgM requires a lower concentration of sC1q to activate the complement compared to pentameric IgM, leading to an increased release of C4 compared to pentameric IgM. The recombinant C1q mimetics competed with sC1q in interaction assays and were able to inhibit complement activation.