Noninvasive evaluation of intragraft immune responses in upper extremity transplantation

In vascularized composite allotransplantation (VCA), invasive tissue biopsies remain the gold standard in diagnosing rejection carrying significant morbidity. We aimed to show feasibility of tape‐stripping for noninvasive immune monitoring in VCA. Tape‐stripping was performed on allografts and native skin of upper extremity transplant recipients. Healthy nontransplanted individuals served as controls. The technique was also used in swine on naïve skin in nontransplanted animals, native skin of treated, transplanted swine, nonrejecting VCAs, and rejecting VCAs. Extracted protein was analyzed for differences in cytokine expression using Luminex technology. Significantly decreased levels of INFγ and IL‐1Ra were seen between human allograft samples and native skin. In swine, rejecting grafts had increased IL‐1Ra compared to naïve and native skin, decreased levels of GM‐CSF compared to native skin, and decreased IL‐10 compared to nonrejecting grafts. Unsupervised hierarchical clustering revealed rejecting grafts separated from the nonrejecting (P = 0.021). Variable importance in projection scores identified GM‐CSF, IL‐1Ra, and IL‐2 as the most important profiles for group discrimination. Differences in cytokine expression are detectable in human VCA patient native skin and VCA graft skin using a noninvasive tape‐stripping method. Swine studies suggest that differences in cytokines between rejecting and nonrejecting grafts are discernable.