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Joined 2026-09-21 Message
Incoming links: Viktor A. Bokisch
Anaphylatoxin 2026-11-05
An anaphylatoxin is a small signaling peptide released from a complement system component during activation. C3a and C5a are important examples: fragments derived from larger circulating proteins act as ligands for cell-surface receptors, connecting complement system activation with cellular responses involved in inflammation.[ref]
The historical name is best understood through measurements of activity. Viktor A. Bokisch and colleagues isolated C3a and measured its ability to contract smooth muscle. Its activity could be inhibited or lost without simply equating every Complement C3 fragment with the same effect. This supplies a concrete example of a protein cleavage product acquiring a signaling role distinguishable from the remainder of its precursor.[ref]
Isolation of a fragment (C3a) of the third component of human complement containing anaphylatoxin and chemotactic activity and description of an anaphylatoxin inactivator of human serum by Viktor A. Bokisch and others. Abstract: isolated C3a, smooth-muscle activity, antibody inhibition and inactivation.
C3a 2026-11-05
C3a is a small protein fragment released when Complement C3 is cleaved during activation of the complement system. It is an anaphylatoxin, associated with inflammatory responses, and is distinct from the larger C3b product involved in surface-associated complement reactions. Proteolysis can thus produce different activities from different parts of one precursor.[ref]
Structures of complement component C3 provide insights into the function and evolution of immunity by Bert J. C. Janssen and others. Introduction and Figure1: C3 activation and fragment organization
In 1969, Viktor A. Bokisch and collaborators isolated C3a by several methods and tested its smooth muscle-contracting activity. Antiserum directed against C3a inhibited the biological response, connecting the isolated fragment to the activity rather than identifying it solely by a separation band. Further enzyme treatment changed its measured activities, showing why the amount of a fragment and its retained function are separate questions.[ref]
Isolation of a fragment (C3a) of the third component of human complement containing anaphylatoxin and chemotactic activity and description of an anaphylatoxin inactivator of human serum by Viktor A. Bokisch and others. Abstract: isolation, smooth-muscle response, antiserum inhibition and enzyme treatment
An idealized bookkeeping example starts with 50 molecules of Complement C3, each undergoing exactly one activation cleavage. It produces 50 C3a fragments and 50 C3b fragments: 100 product molecules, but no doubling of total protein material. In an actual sample, production, further processing and removal all affect the measured concentration of C3a.