High numbers of differentiated CD28null CD8+ T cells are associated with a lowered risk for late rejection and graft loss after kidney transplantation

Background The hypothesis was tested that parameters of an aged T-cell compartment associate with the risk for late rejection after kidney transplantation. Methods Recipients of a kidney transplant in the period 2007-2013 were (N = 365) were included. T cells were characterized prior to transplantation by flow cytometry as naive (CD45RO(-)CCR7(+)), central-memory (CD45RO(+)CCR7(+)), effector-memory (CD45RO(-)CCR7(-)) or terminally differentiated CD8(+) Temra (CD45RO(-)/CCR7(-)/CD28(-)) cells. T cell telomere length and thymic output were assessed prior to transplantation in 202 recipients. Follow-up was until December 2018. The date of the first time of biopsy-proven late rejection (> 6 months after transplantation) was used to calculate the rejection-free survival time. Results Fifty cases of biopsy-proven rejection were recorded. Thymic output and T cell telomere length did not associate with late rejection-free survival. However, the percentage and absolute numbers of CD8(+)Temra and CD28null CD8(+) T cells were significantly lower in patients with late rejection. Specifically, in the highest tertile of percentages of CD28null CD8(+) T cells, the cumulative incidence of late rejection at 5 and 10 years was only 5% and 8% compared to 16% and 20% in the middle to lowest tertile (p = 0.002). Multivariate proportional hazard analysis showed that percentage and absolute number of CD28null CD8(+) T cells remained significantly associated with late rejection and rejection-related graft loss. Conclusion High numbers of differentiated CD28null CD8(+) T cells decrease the risk for late rejection and rejection-related graft loss after kidney transplantation.