Our findings indicate that the presence of particular activating KIRs in donor with their absence in recipient enhances GVHD, which is not accompanied by graft-versus-leukemia effect. Evaluation of activating KIR genotype may allow optimization of both donor selection and transplantation procedure in order to avoid GVHD.

We determined the alleles of 11 mHAs and investigated the association of immunogenic mHA mismatches between a donor and a recipient with a course of allogeneic hematopoietic SCT (allo-HSCT) from 10/10 alleles HLA-matched unrelated donors in 92 recipients after myeloablative conditioning between 2004 and 2006. The frequency analysis of mHA alleles, genotypes and phenotypes accompanied by appropriate restriction HLA Ags allowed for an estimation of the probability of immunogenic mismatches, which was the highest for HA-1, HA-8 and HY. GVH-directed disparity of mHAs with broad tissue distribution, especially of the sex-related HY Ag, influenced the results of allo-HSCT from HLAmatched unrelated donors by not only increasing the probability of chronic GVHD (cGVHD) but also by decreasing the relapse rate.

Factors contributing to relapses and GVHD following allogeneic Hematopoietic Stem Cell Transplantations (HSCT) from HLA-matched unrelated donors are not well established. We analyzed 35 patients (pts) transplanted from HLA 10/10 alleles (A, B, C, DRB1, DQB1) matched unrelated donors (URD) in the Dept. of Hematology and BMT, Katowice, Poland, with use of the same standard operating procedure from January 2004 until March 2006. Indication for HSCT was AML (13 pts), ALL (8), CML (7), MDS (2), PNH (3), CLL (1), myeloid sarcoma (1). Preparative regimen was Treosulfan+Fludarabine (23 pts), TBI+Cy (9) and Bu+Cy (3). Alleles encoding 11 minor Histocompatibility Antigens (mHA: HA-1, HA-2, HA-3, HA-8, HB-1, ACC-1, ACC-2, HwA-9, HwA-10, UGT2B17, HY) were analyzed for each donor-recipient pair with use of Dynal AllSet mHA typing kit and PCR-SSP method. Only immunogenic mHA mismatches were analyzed. Information on whether mHA mismatches might result in Host-versus-Graft or Graft-versus-Host responses was established with use of the minor Histocompatibility Knowledge Database of Leiden University Medical Center’s minor Histocompatibility Workshop. Patients transplanted from donors with mHA mismatched in HVG direction had significantly higher probability of relapse (64+/− 8% versus 10+/− 9%, p=0.003) when compared to pairs without mHA HVG immonogenicity. Patients transplanted from donors with mHA mismatched in GVH direction had higher probability of aGVHD (88+/− 8% versus 53+/− 11%, p=0.14) and cGVHD (41+/− 16% versus 37+/− 17%, p=0.65) when compared to pairs without GVH immunogenicity. GVHD was also observed more often on day +100 (33% versus 6%, p=0.06) when mHA mismatch in GVH direction was present. Observed influence of HVG and GVH immonogenicity on probability of relapse and GVHD did not lead to significantly different survival in observed groups of pts. These results indicate that mHA immunogenic mismatches in HVG and GVH direction may be responsible for relapse and GVHD, respectively, in HSCT recipients from HLA-matched unrelated donors. The study is being continued to confirm these primary observations and to establish the associations of specific mHA mismatches with HSCT outcomes. Impact of mHA mismatch on probability of relapse and GVHD Immunogenicity of mHA mismatches HVG no HVG p # of patients 18 17 Relapse at 1 year 64%+/−8 10%+/−9 0.003 Immunogenicity of mHA mismatches GVH no GVH p # of patients 16 19 aGVHD 88%+/− 8 53%+/−11 0.14 cGVHD at 1 year 41%+/−16 37%+/−17 0.65 Impact of mHA mismatch on probability of survival Immunogenicity of mHA mismatches HVG GVH only HVG only GVH no HVG no GVH p # of patients 9 9 7 10 Survival at 9 months 63%+/−17 57%+/−25 83%+/−15 69%+/−15 0.86

a c t a h a e m a t o l o g i c a p o l o n i c a 4 5 ( 2 0 1 4 ) 3 6 0 -3 6 9

Acute myeloid leukemia (AML) with fetal liver tyrosine kinase 3 (FLT3) internal tandem duplication (ITD) is associated with poor prognosis, and allogeneic stem cell transplantation (Allo-SCT) seems to be the preferred therapeutic approach. However, the predictors of post-transplant outcomes were not well-defined. The aim of the study was to evaluate the significance of FLT3/ITD mutation by polymerase chain reaction as minimal residual disease (MRD) marker of outcomes after transplantation. We identified 43 patients (28 females and 15 males) with FLT3-mutated AML at the median age of 45 years who were allografted between 2009 and 2019. Hematological status at transplant was as follows: the first complete remission (CR1) in 29 patients, CR2 in 5, and 9 patients were transplanted in marrow aplasia (MA). Twenty-seven patients were FLT3 MRD negative at transplant. Median time from diagnosis to transplant was 16.7 months. Post-allograft CR rate was 88%. The relapse incidence (RI) was lower for patients who were FLT3 MRD negative at transplant when compared with those with FLT3 MRD positivity (41% vs 59%; p = 0.01). The patients who eradicated FLT3/ITD at day + 30 after transplant had lower RI than those with detectable FLT3/ITD (23% vs 76%; p = <0.001). The 2-year LFS and OS were 53% and 54%, with the median OS and LFS of 28 months and 27 months, respectively. Patients with CR1/2 and FLT3 MRD(−) had a 2-year OS of 80%. The FLT3 MRD negativity at transplant prolonged LFS in multivariate analysis (HR 5.3 95%CI 1.97-14.2); p < 0.001), whereas FLT3 MRD negativity and unrelated donor predicted favorable OS.