Origin of L angerhans cells in normal skin and chronic GVHD after hematopoietic stem‐cell transplantation

Chronic graft‐versus‐host disease (c GVHD ) is a common complication following allogeneic stem‐cell transplantation ( SCT ). Past studies have implicated the persistence of host antigen‐presenting cells ( APC s) in GVHD . Our objective was to determine the frequency of host L angerhans cells ( LC s) in normal skin post‐ SCT and ask if their persistence could predict c GVHD . Biopsies of normal skin from 124 sex‐mismatched T ‐cell‐replete allogenic SCT recipients were taken 100 days post‐transplant. Patients with acute GVHD and those with <9 months of follow‐up were excluded and prospective follow‐up information was collected from remaining 22 patients. CD 1a staining and X and Y chromosome in‐situ hybridization were performed to label LC s and to identify their host or donor origin. At 3 months, 59 ± 5% of LC s were host derived. The density of LC s and the proportion of host‐derived LC s were similar between patients that did or did not develop c GVHD . Most LC s in the skin remained of host origin 3 months after SCT regardless of c GVHD status. This finding is in line with the redundant role of LC s in acute GVHD initiation uncovered in recent experimental models.