Introduction
Vascularized composite allografts (VCA) such as hand allografts, contains large amount of most immunogenic skin component Multiple acute rejection episodes in the majority of human VCA routinely target skin while sparing other tissue types Skin dendritic cells (DCs) are thought to play critical roles in either initiation or regulation of skin immunity However, their contribution to the unique alloimmune response and acute skin rejection of VCA is still largely unknown This study seeks to characterize the spatiotemporal dynamics of skin resident DCs at different stages of rejection after hind-limb transplantation and to better understand the role of skin DCs in immunomodulation of VCA.
Materials and methods
Lewis rats received allogeneic hind-limb transplants from BN rats without immunosuppressive treatment, and were inspected daily for their clinical signs of rejection using a visual scoring system Recipients were sacrificed at different time points post-transplantation Allograft skin, adjacent recipient skin, and draining lymph nodes were harvested and processed to obtain single cell suspension for flow cytometric analysis, or to extract total RNA and proteins and assessed by real-time PCR and Luminex.
Results
1) We developed a new technique for isolation and characterization of skin DCs in rat hind-limb transplant model 2) Skin resident lymphocytes and distinct subsets of skin migratory DCs: Langerhans cells (LCs), dermal DCs (DDCs), and langerin+ DDCs, in the transplanted limb were identified and enumerated 3) Skin migratory DCs in both allograft and recipient limb skin showed different patterns of change with increasing severity of rejection 4) The expression of Th1-, Th2-, Th17-, and Treg- associated genes and cytokines in allograft and recipient limb skin exhibited dynamic changes and temporal correlation with the quantity of skin DCs during the process of rejection.
Conclusions
The correlative trends between skin DC subsets and T cell-mediated alloimmune response suggest a complex cutaneous immune cell network modulated by skin DCs in VCA By understanding the dynamics of skin DCs and their influence on the T-cell response, the novel targeted immunomodulation therapy can be developed for VCA.
Funding
This work was supported by American Association of Plastic Surgeons Academic Scholarship.