Nikolett Lupsa1,2, Barbara Ersek1,3; Andor Horváth1; Andras Bencsik1; Eszter Lajkó1; Adam Oszvald1, Zoltan Wiener1, Tamas Masszi4,5, Peter Remenyi6, Gabor Mikala6, Edit Buzas1,2, Zoltan Pos1
1 Semmelweis University, Genetics, Cell and Immunobiology, Budapest, Hungary
2 Hungarian Academy of Sciences - Semmelweis University, Budapest, Hungary, Immunoproteogenomics Extracellular Vesicle Research Group, Budapest, Hungary
3 Hungarian Academy of Sciences, Office for Research Groups Attached to Universities and Other Institutions, Budapest Hungary
4 St. Istvan and Saint Laszlo Hospital, Department of Hematology and Stem Cell Transplantation, Budapest, Hungary
5 Semmelweis University, 3rd Department of Internal Medicine, Budapest Hungary
6 South Pest Center Hospital, National Haematological and Infectious Institute, Hematology and Stem Cell Transplantation, Budapest Hungary
Introduction: Perturbation or dysregulation of T cell homing is often involved in several autoimmune or inflammatory diseases. Further exploration of this phenomenon may lead to a better understanding of multiple immunological disorders.
Aim: This study sought to identify novel markers of skin- and gut-homing CD8+ T cells by analyzing them in acute graft versus host disease (aGvHD), typically involving CD8+ T cell-mediated organ damage of the skin and gut.
Method: Patients undergoing allogeneic hematopoietic stem cell transplantation were assigned to groups developing cutaneous aGVHD, gastrointestinal aGvHD, both, or none, and their sorted skin-homing (CD8+/CLA+), gut-homing (CD8+/integrinβ7+), and reference (CD8+/CLA-/integrinβ7-) T cells were compared by microarray analysis. Gene expression validations were done by Q-PCR and flow cytometry. Functional tests were performed by pull-down assay, proteome profiler array and inhibitor screening tests.
Results: We found increased expression of PI16 in skin-homing CD8+ T cells both at RNA and protein level. PI16 was expressed by CD8+ T cells regardless of the organ(s) affected by aGvHD, and remained associated to skin-homing T cells in healthy blood donors, too. PI16 was found largely T cell-restricted, and was confined to the non-naïve CD45RO+ compartment. Induction of PI16 expression was independent of vitamin D3 and retinoic acid, or by co-culture with human skin and intestinal organoids. PI16 appeared GPI-anchored on the plasma membrane and became lost upon re-stimulation of circulating skin-homing T cells. Loss of PI16 occurred by rapid downregulation of PI16 transcription, not by PLC- or ACE-mediated shedding, or by recycling from the plasma membrane. Inhibitor screening and pull-down experiments confirmed that PI16 has low affinity, if any, to most skin proteases, but inhibits cathepsin-K.
Conclusion: These data demonstrate robust PI16 expression in skin-homing CD8+ T cells, and raise the possibility that PI16 may inhibit an inflammatory skin protease until cutaneous CD8+ T cell activation.
Doctoral School: Doctoral School of Molecular Medicine
Program: Basis of Human Molecular Genetics and Gene Diagnostics
Supervisor: Zoltan Pos