Abstract
Abstract We separated 19S IgM from mixed IgM-IgG cryoglobulins at pH 4.1 on Sephadex G-200; the IgM obtained by this procedure showed strong anti-γ-globulin activity for both human and rabbit γ-globulins and formed cryoprecipitates with rabbit as well as human IgG after incubation at 4 ° C. The 19S IgM derived from mixed cryoglobulins was radioiodinated, and metabolic degradation was studied following intravenous injection into rabbits. In vivo decay and organ distributions were compared to control, serologically negative 19S IgM prepared from patients with Waldenstrom's macroglobulinemia. Disappearance curves for labeled control and 19S rheumatoid factor IgM were very similar, and half-life (t12)-values were 26.3 and 25.7 hours, respectively. The liver and kidney showed increased amounts of radioactivity as did the lung in most instances; highest counts were detected in spleens from rabbits injected with IgM derived from patients with vasculitis associated with their cryoglobulinemia. Following in vitro incubation and intravenous injection of of IgM-I 125 , 5 hour ultracentrifugation of rabbit serum samples on sucrose density gradient was done. Assay of fractions for radioactivity indicated that during the brief centrifugation, human cryoglobulin IgM did not separate from rabbit serum proteins following in vitro incubation. In sharp contrast, assay for I 125 in serum from rabbits injected with serologically active IgM derived from mixed cryoglobulins revealed the presence of rapidly sedimenting radioactive material, presumably the rheumatoid factor complexed with rabbit IgG. Rapidly sedimenting labeled IgM was not detected in animals injected with control serologically negative human IgM.
Published Version
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