Type 1 IFN levels, pharmacodynamics response, and cellular immune subsets. (A) Paired plasma levels of IFN-α in recipients (n = 12) at baseline (preconditioning [Pre]), as well as at day 28 (D28) and day 56 (D56), were analyzed by Luminex array. (B) Frequency of pSTAT1 protein (n = 8) within CD45⁺ cells measured by fluorescence-activated cell sorting (FACS) in paired samples from donors and recipients at day 28 and day 56. (C) The numbers of CD141⁺CLEC9A⁺ DCs (n = 3) were measured by FACS from donors and recipients at day 28 and at day 56. (D) The numbers of WT1⁺CD8⁺ T cells by WT1-specific dextramers (n = 3) in patients with HLA-A*0201. Analysis was performed by FACS in paired donors and recipients at days 28, 56, 100, and 180 after HCT. Samples obtained after relapse or high-dose corticosteroids for GVHD were excluded. Data are mean values; error bars represent the standard error of the mean. *P < .05, **P < .01, paired Student t test.