Calreticulin surface expression (cs-CRT) and extracellular serum CRT levels in patients with AML. (A) Leukemic cells from patients with AML at diagnosis and myeloid cells from 75 healthy volunteers were CD45⁺ gated and CD33⁺/CRT⁺ cells were determined. (B) Immunoprecipitation of serum from 2 patients with AML (#5 and #6) and 1 healthy volunteer (H1) demonstrated the 55-kDa wild-type CRT and a smaller 27-kDa peptide. (C) CRT concentration in serum from 113 patients with AML at diagnosis and from 86 healthy volunteers was investigated by C-terminus and N-terminus specific CRT ELISA. (D) cs-CRT and N-terminus CRT serum concentrations of AML patients at diagnosis were studied for correlation. (E) CRT on the cell surface by flow cytometry and (F) N-terminus CRT in the serum by ELISA were assessed in 3 de novo AML patients (#1 and #4 had FAB type -M1, and #2 had -M4Eo) during the first 30 hours of chemotherapy in induction cycle 1. Anthracyclin (anth; idarubicin 12 mg/m²) was given over 3 hours and cytarabine (cyt; 200 mg/m²) over the following 21 hours.