Figure 3.

Dynamic course of ADAMTS13-related parameters in three patients with acquired TTP. The dynamic course of ADAMTS13:Ac, ADAMTS13:Ag, ADAMTS13 functional inhibitor, free IgG anti-ADAMTS13 antibody titers and ADAMTS13-specific immune complexes (ICs) was analyzed in three patients who experienced one (A) or two (B–C) acute events with subsequent clinical remission within the observation period. For each patient, treatment with plasma exchange (PEX), corticosteroids (CS), splenectomy or rituximab is indicated. The immunoblots show the ADAMTS13-specific ICs of the IgG class as determined by co-immunoprecipitation. Pooled normal human plasma (NP) served as a negative control. The bands of ~160 and ~140 kDa seen in (B) for some time points most likely represent cleavage fragments of ADAMTS13, as fragments of equal molecular weight were obtained after digestion of rADAMTS13 with plasmin (data not shown). Similar findings were obtained by Feys et al.⁴⁴ in samples of plasma from a patient with acquired TTP. The position of ADAMTS13 in the gel (~190 kDa) was determined by loading 5 ng of rADAMTS13 (rA13). Ac: acute event. The lower panel of each blot shows the corresponding free and complexed anti-ADAMTS13 antibody titers as detected by ELISA, as well as ADAMTS13:Ac, ADAMTS13:Ag and inhibitor titers. ADAMTS13:Ac and ADAMTS13:Ag levels over 0.5 U/mL and 403 ng/mL are considered normal. For ADAMTS13:Ac, a dash denotes levels <0.10 U/mL (<10%). A dash denotes an undetectable level. ND: not determined.