Immunoglobulin M: Fixation of Human Complement by the Fc Fragment

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Science  07 Apr 1972:
Vol. 176, Issue 4030, pp. 55-56
DOI: 10.1126/science.176.4030.55


The Fc fragment [(Fc)5µ with a molecular weight of 342,000] of human immunoglobulin M from patients with Waldenström's macroglobulinemia has a complement fixing ability approximately 19 times greater on a molar basis than that of the parent immunoglobulin M. This fragment, which occurs naturally as a pentamer fixes human but not guinea pig complement, and this activity remains unchanged even after the fragment is reduced to the monomeric form.