Plasmacytoid Dendritic Cells and Chemokine Milieu in Human Cutaneous Chronic-Graft-versus-Host-Disease

Objectives: Antigen-presenting cells, including plasmacytoid dendritic cells (pDCs), are believed to be critical for initiation of the graft-versus-host reaction following allogeneic hematopoietic stem cell transplant, and in shaping the disease character in subsequent chronic graft-versus-host disease (cGVHD). Skin and oral mucosa are primary sites of cGVHD (sclerotic or lichenoid forms). The present pilot study was designed to define the microenvironment in sclerotic versus lichenoid patient samples.

Methods: Immunohistochemistry (IHC) targets were selected from an earlier microarray study. A subset of patients from the initial cohort with sclerotic(n=10) or lichenoid(n=4) cGVHD or healthy volunteer(HV, n=4) were included from cutaneous biopsies (clinicaltrals.gov study NCT00092235). Formalin-fixed, paraffin-embedded tissue was prepared, stained for pDCs, T cells, and immune molecules, and imaged on a Nikon Eclipse Ti confocal microscope. Image analysis with Volocityx64 software calculated expression of MxA and CXCL10 within a region of interest that included equal epithelium and subepithelial tissue depth, then normalized by total surface area analyzed.

Results: More CD3⁺T-cells and CD3⁺/MxA⁺ cells were detected in cGVHD skin with an increase in lichenoid versus sclerotic specimens (p=0.05, Kruskal-Wallis, Dunn’s]. Higher total MxA expression was detected in lichenoid versus sclerotic skin (p=0.05,1-way ANOVA, Tukey’s). CXCL10 was elevated in both sclerotic and lichenoid patients with no difference between cGVHD groups. Finally, pDCs(CD123⁺/CD303⁺/CD3^-) were detectable in 50% of HVs,70% of sclerotic samples, 75% of lichenoid samples.

Conclusions: T-cells, pDCs, MxA and CXCL10 expression were confidently detected in cGVHD skin using fluorescent IHC. The immune cell infiltrate suggests T-cell, MxA and CXCL10 involvement in both sclerotic and lichenoid forms of cGVHD, with differential involvement of pDCs. These data support future efforts to define the role of pDCs at barrier sites in cGVHD.