title: Immunoglobulin M: fixation of human complement by the Fc fragment.
abstract: The Fc fragment [(Fc)(5)micro 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.
mesh_terms: D000818:Animals; D001665:Binding Sites; D002852:Chromatography, Ion Exchange; D003168:Complement Fixation Tests; D006168:Guinea Pigs; D006801:Humans; D007074:Immunoglobulin G; D007075:Immunoglobulin M / Q000032:analysis*; D007136:Immunoglobulins / Q000032:analysis*; D008970:Molecular Weight; D008258:Waldenstrom Macroglobulinemia / Q000276:immunology
chemical_list: D007074:Immunoglobulin G; D007075:Immunoglobulin M; D007136:Immunoglobulins