This is a prospective cohort observational study to assess the role of AlloSure Donor Derived Cell Free DNA (ddcfDNA) assay in the monitoring of three high-risk groups of kidney transplant patients for antibody mediated processes.

• Group A. Thirty participants with a positive Virtual Cross-Match (VXM) at the time of transplant will be monitored for 12 months
• Group B. Similarly, 24 participants with dnDSA will undergo a SOC biopsy within approximately three months to determine the incidence of Active Antibody Mediated Rejection (AMR)
• Group C. 15 additional participants with the diagnosis of Chronic Active Antibody Mediated Rejection (cAMR) will undergo standard of care therapy and be monitored for treatment response with a follow-up biopsy at three months

This is a prospective cohort observational study to assess the role of AlloSure Donor Derived Cell Free DNA (ddcfDNA) assay in the monitoring of three high-risk groups of patients for antibody mediated processes.

The AlloSure assay will be combined with the AlloMAP assay (PAXgene blood sample); which is the first in history FDA-cleared genomic solid organ transplantation rejection blood test (AlloMap). Immune cell phenotypes and inflammatory cytokines will be examined. The combination of the three assays will provide a comprehensive molecular diagnostic and prognostic approach to antibody-mediated processes after renal transplantation. Additionally, formalin fixed paraffin embedded (FFPE) samples from kidney biopsies for subjects in all groups will be used to validate the nCounter platform. 3 slides from each biopsy will be sent to CareDx to be examined on the nCounter system. Other routine clinical data will be examined and assessed for correlation with the nCounter results. This will include AlloSure, Molecular Microscope, eGFR, creatinine, DSA as well as other key data fields taken from the Electronic Medical Record (EMR).

AlloMap Kidney is a lab-developed test and will be provided by CareDx, Inc. located at Brisbane, CA, and is designed, manufactured and used within a single CareDx laboratory. AlloMap Kidney is currently provided as "For Research use only" test and results are not intended for clinical diagnosis or patient management for "KidneyCare", which is the AlloSure-Kidney and AlloMap-Kidney tests combined.

• Group A. Thirty participants with a positive VXM at the time of transplant will be monitored for 12 months and undergo protocol biopsies on months 3 and 12 to detect subclinical rejection. Participants may also undergo clinically indicated biopsies for suspicion of rejection. AlloSure, AlloMap, immune cell phenotypes, and inflammatory cytokines will be measured at baseline (within 48 hours of transplant), 3 weeks, 6 weeks, 3M (SOC biopsy), 6M, 12M (SOC biopsy) and additionally at the time of any indication biopsy (5-7 time points/patient). Subjects in this group will be monitored for 12 months.
• Group B. Similarly, 24 participants with dnDSA will undergo a SOC biopsy within approximately three months to determine the incidence of AMR. Immune cell phenotyping, AlloSure and AlloMap will be measured at the time of the SOC biopsy (1 timepoint/patient). This is a single-time point study, unless participants are diagnosed with AMR and require treatment. In this case, they would be enrolled in group C (see below).
• Group C. 15 additional participants with the diagnosis of cAMR will undergo standard of care therapy and be monitored for treatment response with a follow-up biopsy at three months. Immune cell phenotyping, AlloSure and AlloMap will be used at baseline (prior to index biopsy) and 3M (follow-up surveillance biopsy) (2 timepoints/patient). Participants in this group will be monitored per SOC for three months (time between the two biopsies).

For all three groups, history and physical, blood draws and urine sample collections are performed per SOC. The only addition is blood sample collection and additional urine collection at the indicated SOC timepoints for AlloSure, AlloMap, immune cell flow cytometry, RNA-signatures, and inflammatory cytokines. In addition, leftover pathology slides that are stored in the pathology department will be sent out to CareDx for the purposes of performing the NanoString analysis. The slides will be returned to the pathology department after the NanoString analysis is complete.

Inclusion Criteria:

• Kidney transplant recipients (de novo or retransplant)
• Positive Virtual Crossmatch at transplant (Group A)
• Undergoing SOC biopsy for dnDSA (Group B)
• Proven cAMR (Group C)

Exclusion Criteria:

• Multi-Visceral transplant
• Contraindication to renal biopsy

Kidney Transplant Recipients