Association of donor-specific microchimerism with graft dysfunction in kidney transplant patients

The biological significance of donor-specific microchimerism (DSM) in solid organ transplantation is unresolved. It has been reported both as a favourable feature, which may facilitate induction and maintenance of tolerance, and as a sign of graft-vs-host disease. Here, we applied a quantitative real-time PCR assay (qRT-PCR) to a selected series of kidney transplant recipients to measure the level of microchimerism in relation to allograft function and survival. DSM level was assessed by scoring the HLA-DRB1 locus in 54 patients (42 males, 12 females) with more than 2 years of follow-up after transplantation; 38 patients were considered to have stable renal function (SRF) and 16 had allograft dysfunction (AD). Among patients with AD, 12 (75%) showed detectable level of microchimerism, compared to 11 (29%) SRF patients (Odds Ratio 7.36, 95% CI 1.7–35.2; p < 0.01). In addition, AD patients showed a higher mean donor genome equivalents (6.5 × 10− 5 vs. 2.4 × 10− 5; p < 0.001). SRF patients were re-evaluated two years later; 2 out of 27 DSM negative vs. 2 out of 11 DSM positive had lost their transplanted organ. In conclusion, qRT-PCR applied to peripheral blood shows significant association between DSM and allograft dysfunction in kidney transplant patients.

► Role of Donor-Specific Microchimerism (DSM) in solid organ transplants is unclear.
► Quantitative real-time PCR (qRT-PCR) is a reliable method to measure DSM.
► Among 54 kidney transplanted patients, 16 (30%) showed allograft dysfunction (AD).
► The chance of observing DSM was about 7-fold higher in the AD patients (p < 0.01).
► The mean donor genome equivalents was 3-fold higher in the AD patients (p < 0.001).