(A) Pre- and post-transplant plasma values for haptoglobin; LDH; free Hb concentration; nitric oxide (NO) consumption; sVCAM-1; and arginine/ornithine ratio. Median levels for each parameter are represented by the black filled diamonds. The dotted line represents the upper limit of the range of normal for each parameter. For each parameter, at least two post-transplant samples, obtained at the time of mixed chimerism, were measured per patient, and each symbol represents the mean of two or more measurements per patient. Plasma haptoglobin was measured immunonephelometrically (Behring Nephelometer II, Newark, DE, USA). Total bilirubin (panel B) and LDH were measured using a Hitachi Autoanalyser (Roche Diagnostics, Indianapolis, IN, USA). Plasma arginine and ornithine were measured by ion exchange chromatography (Hitachi Amino Acid Analyser L-8800; San Jose, CA, USA). Plasma sVCAM-1 levels were measured by ELISA (R&D Systems, Minneapolis, MN, USA). Plasma free haemoglobin and NO consumption were measured as previously described (Reiter et al, 2002). For all parameters, upper range of normal was defined as two standard deviations above the average of values obtained from 30 normal donors. On the seven of nine patients for whom both pre- and postsamples were available, paired analysis using the two-sided Wilcoxon signed-rank test was performed. (B) Serial plasma measurements of parameters of intravascular haemolysis and endothelial function following HSCT in the setting of sustained donor engraftment following immunosuppressive taper (patients 4 and 6), and late graft rejection (patients 1 and 3). Shown are measurements of donor chimerism (overall donor chimerism denoted by the dashed line; erythroid lineage specific chimerism denoted by the solid line); total bilirubin; haptoglobin; NO consumption; free Hb concentration; sVCAM-1; LDH and arginine/ornithine ratio (only collected from patients 4 and 6) following HSCT. The fine dotted line represents the upper limit of the range of normal for each parameter. For patient 3, erythroid lineage-specific chimerism measurements were unavailable; the % HbS levels are shown, represented by grey circles and lines.