Recipient chimerism after R−/D− HSCT is greater than that after R−/D+ HSCT, but significantly less than after R+/D− HSCT. Comparison of chimerism levels according to recipient/donor serostatus in the sibling donor cohort. The horizontal bars indicate the respective medians. Statistical comparisons (R−D+ vs R−D−; R−D− vs R+/D−; R−D+ vs R+D+; R+D+ vs R+/D) were performed using a 1-tailed Mann-Whitney U test. Statistical comparisons between R−/D− and R+/D+ were performed using a 2-tailed Mann-Whitney U test.