Factor Bb and the relative concentration of C3b₂-IgG complexes in plasma of ADM and DM patients treated with 2 g IVIG/kg body weight. Plasma samples were drawn from 2 amyopathic (A-B) and one myopathic patient (C) during the first IVIG treatment at the times indicated. IVIG infusion was completed by 33 hours in patient G (B) and patient F (C), and by 48 hours in patient B (A). Plasma samples were either freshly frozen for factor Bb determination (▪) or denatured within 75 seconds from collection for quantification of C3b₂-IgG complexes (♦, thin line). C3b₂-IgG complexes were quantified from one-dimensional immunoblots incubated with labeled mAb H206. Immunoblotting data were averaged from 2 or more (with SD) blots and normalized to the pretreatment value.