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Joined 2026-09-21 Message
Incoming links: Complement system
Complement system 2026-10-18
The complement system comprises immune proteins; its components provide an interaction partner for Fc fragments.
Fragment crystallizable region 2026-10-18
The Fc fragment comprises paired immunoglobulin heavy chain portions, interacts with immune partners and lacks paratopes. Its name records historical crystallization.[ref]
The structure of a typical antibody molecule. Immunobiology: The Immune System in Health and Disease, 5th edition by Charles A. Janeway, Jr. and others; §3-3: crystallization-based name, paired CH2 and CH3, and effector interactions
For example, Fc fragments can bind components of the complement system, illustrating a function distinct from epitope recognition.[ref]
Antibody Structure and Molecular Immunology by Gerald M. Edelman. Antibody Structure and Molecular Immunology, printed p. 37: Fc binding to complement components
An isolated Fc fragment therefore separates one set of protein interactions from target recognition. In the connectivity example under Papain digestion of IgG, the Fc fragment contributes one connected product but zero antibody binding sites. Retaining it preserves different interaction surfaces; it does not restore either severed arm. Conversely, the two Fab fragments preserve the stipulated epitope-recognition sites while losing their connection to this common stem.