Association of Skin and Blood Dendritic Cells with Acute Graft Versus Host Disease after Human Haematopoetic Cell Transplantation.

Both number and origin of dendritic cells (DC) in the blood have been associated with acute graft-versus-host disease (aGvHD), graft-verus-leukemia effect, relapse and graft failure after human allogeneic haematopoietic cell transplantation (aHCT). Aim of this study was the systematic simultaneous investigation of skin and blood DC subtypes, the analysis of their host/recipient origin after HCT and the correlation of DC kinetics with treatment, outcome and incidence of aGVD and its treatment in 31 recipients of allogeneic HCT. Epidermal shave biopsies and peripheral blood samples were collected from patients pre and at defined time points following aHCT, DC from skin and blood isolated and examined by FACS and quantitative PCR for Short Tandem Repeat markers. A significant reduction in number of skin and blood DC subtypes was observed already before start of conditioning chemotherapy in patients compared to healthy volunteers. A majority of donor derived epidermal Langerhans Cells (median 95%, range 53–100%) and also dermal DC (median 94%, range 39–100%) was found in all examined patients even early after transplant independent from chemotherapy regimen, graft, occurrence of skin GvHD or time point after transplantation. Numbers of both skin DC subsets remained low for months post HCT. Reconstitution kinetics of CD 11c⁺ preDC1 and CD 123⁺ preDC2 blood DC were similar to each other and pre transplant numbers were reached again around day +112 post transplant. Recipients of grafts containing higher T cell numbers had lower preDC1 counts on day +28. PreDC2 reconstitution was negatively affected by steroid treatment. Patients with aGvHD tended to have more preDC1 on day +28 and lower numbers of both preDC subsets on day 56 post transplant. Residual host blood DC were rare at all time points (median <3% at all investigated timepoints range 2–97%). The kinetics of DC reconstitution at different sites might become an important diagnostic tool to predict the occurrence of acute and chronic GvHD and to monitor the efficacy of prophylactic and therapeutic interventions.