This study will focus on each individual patient from the early point of myeloablative conditioning through HSCT and GVHD. The rationale for this individualized approach is to account for the anticipated variability in patient age and primary disease, background pathology and individual therapeutic course, considering the enormous heterogeneity of this condition. To compensate for this limitation, we intend to create an individualized algorithm, based on a novel dynamic biomarker, i.e., AAT functionality, individualized per patient and placed on a timeline, with the aim of minimizing future occurrences of GVHD, and by using readily available laboratory measurements. The study is designed around patient sample collection, there is no change in standard of care, therefore there is no intervention as well.