Metabolism of Human γ-Macroglobulin (IgM) in Normal Man

Abstract

A method for isolation of radioiodine-labelled IgM by means of Sepharose 4 B gel filtration is described. In studies of 28 control subjects, 11 females and 17 males, normal, polyclonal IgM was catabolized by a first order process, with a rate of 7.5–14.5 (mean 10.6) per cent of the intravascular mass per day. More than 74 per cent of the total exchangeable IgM was localized in the intravascular pool, i.e. 8.3–51.1 (mean 22.8) mg per kg. From 0.7 to 5.1 (mean 2.2) mg of IgM was synthesized per kg per day. Monoclonal IgM, in five turnover studies, was catabolized at the same rate as polyclonal IgM. IgM preparations obtained by three different isolation procedures were catabolized at the same rate.