IL-17 producing cells home to the graft early after heart transplantation

Annemiek Peeters¹, Marjolein Dieterich¹, Kadir Caliskan², Lex Maat³, Aggie Balk², Willem Weimar¹, Carla C. Baan¹, Nicole van Besouw¹

¹Department of Internal Medicine - Transplantation; ²Department of Cardiology; ³Department of Thoracic Surgery; Erasmus MC, Rotterdam, The Netherlands

Purpose: While IL-17 is predominantly a proinflammatory cytokine, it has pleiotropic and environmental specific functions. Therefore, it is tempting to speculate that IL-17 is important in inflammatory responses seen in organ transplant patients. We determined IL-17 mRNA expression in the transplanted heart and donor-specific IL-17 producing cells in peripheral blood cells during early and late acute rejection episodes, and during immunological quiescence after heart transplantation.

Methods and materials: Endomyocardial biopsies (n=41) from heart transplant recipients (n=29) who experienced an early or late acute rejection were analysed for the presence of IL-17 mRNA. Moreover, we determined the frequency of donor-specific IL-17 producing peripheral blood cells by Elispot assay (n=35).

Results: Twenty-two percent (9/41) of the biopsies were positive for IL-17 mRNA. All (9/26) were observed in the early period (£3 months) after transplantation, while none (0/15) of the late (>3 months) biopsies expressed IL-17 mRNA (p=0.02). During early acute rejection, 56% (5/9) of the biopsies did express IL-17 mRNA, while biopsies from late acute rejections (0/5) did not express IL-17 mRNA (p=0.09). In contrast to the findings in the graft, we detected donor-specific IL-17 producing cells in peripheral blood predominantly late after transplantation (early 1/15 vs. late 7/20, p=0.10).

Conclusion: Early after transplantation IL-17 producing cells may home to the graft contributing to the rejection process, while late after transplantation this homing phenomenon does not occur.