Relative changes of C3 and C4 concentrations in plasma of IVIG-treated patients with ADM. C3, C4, and α₂-macroglobulin (α₂M) were determined at the given time points in freshly frozen plasma drawn from 3 amyopathic patients and patient F with DM, having low CK activity. All patients received the first course of IVIG treatment (2 g IgG/kg body weight during the first 2 days). The C3 and C4 concentrations were corrected for blood volume changes by calculating ratios (C3/α₂M; C4/α₂M) and normalized to the pretreatment values. Averaged values are shown with ± 1 SD for C3 (•) and C4 (□). Data are plotted in a logarithmic time course with the pretreatment values set to 0.01 days.