*2.2. Patient Characteristics of Cross Sectional and Longitudinal AR Study Population*

Next, we sought to investigate the relation of circulating lncRNAs with AR. To that end, we included plasma samples of a different cross-sectional study cohort that included patients with acute T cell mediated rejection and a control group of patients with stable kidney transplant function after transplantation (hereafter mentioned as 'stable'). In addition, AR patients were studied longitudinally at 6 and 12 months after rejection to determine the dynamics after AR. The baseline characteristics of the transplant recipients in this cohort are described in Table 1. Most common causes of initial kidney failure before transplantation were autosomal dominant polycystic kidney disease (23%), focal segmental glomerulosclerosis (17%) and IgA nephropathy (13%). The mean time after transplantation (12 months) was comparable. Immunosuppressive regimen did not differ significantly. eGFR was lower and proteinuria higher in patients with AR, compared with stable patients (resp. *p* < 0.001 and *p* = 0.003). Factors that can influence the amount of vascular injury next to rejection, such as donor age, dialysis before transplantation, and months since transplantation, did not differ significantly. Incidence of active smokers was 7% in AR patients and 13% in stable patients. Panel reactive antibodies (PRA), mismatch, immunosuppressive regimen and the presence of previous transplantations did not differ between stable patients and patients with AR. Patients with AR had interstitial rejection, with or without involvement of the vasculature, and were treated with methylprednisolone (67%), ATG alone (13%), or a combination of methylprednisolone and ATG (13%) or alemtuzumab (13%).

**Figure 1.** Decreased capillary density after acute rejection. (**A**) Representative images of CD34 staining for pre-transplantation and acute rejection (AR) biopsies. (**B**) Quantification of CD34 staining (PreTx, *n* = 78; AR, *n* = 102). (**C**) Representative images of CD73 staining for pre-transplantation and acute rejection (AR) biopsies. (**D**) Quantification of CD73 staining (PreTx, *n* = 66, AR, *n* = 29). \*\*\* *p*-value < 0.001.

**Table 1.** Cross-sectional study patient characteristics of patients with a stable kidney transplant function (stable) and patients with acute rejection (AR).



**Table 1.** *Cont.*

<sup>1</sup> Fisher's exact test, <sup>2</sup> unpaired t-test, <sup>3</sup> Mann-Whitney U test, KTx = kidney transplantation, PRA = panel reactive antibody.
