IFN-γ secretion is suppressed whereas IL-6 is dysregulated after clinical SCT. Plasma (A) IFN-γ and (B) IL-6 levels were measured prior to SCT conditioning (day −7) and up to day 90 post-SCT while receiving calcineurin-based immune suppression (CsA or tacrolimus and MTX). IFN-γ levels after transplant (beyond day 0) are not significantly different to that of pre transplant (day −7). IL-6: ***P = .0007 vs day +7. (C) Plasma IL-6 levels in HLA-matched (n = 29) vs HLA-mismatched (n = 21) recipients at day +7 post-SCT. (D) Plasma IL-6 levels at day +7 post-SCT in recipients receiving either TBI (n = 12) vs reduced intensity conditioning (fludarabine/melphalan; n = 38). **P = .003.