Genomic DNA extraction and microchimerism analysis by ddPCR
BLOOD
Genomic DNA was extracted from peripheral blood (PB) and cerebrospinal fluid (CSF) samples using the Qiamp DNA Blood or Qiamp DNA micro kits (51104 and 56304, Qiagen), checked for purity using a NanoDrop spectrophotometer (Thermo Fisher Scientific), quantified using the Qubit dsDNA HS Assay Kit (Q32851) according to the manufacturer’s protocol and then stored at −20 °C for further analyses. To identify informative polymorphisms for the subsequent microchimerism analysis, donor-derived and patient-derived genomic DNA were screened using the quantitative PCR (qPCR)-based KMRtype genotyping assay (8841781, GenDx), according to the manufacturer’s recommendations. The kit covers 39 bi-allelic markers distributed over 20 different chromosomes, multiplexed in ten different assays. Based on the results, donor-specific (positive in the donor and negative in the patient) and patient-specific (positive in the patient and negative in the donor) markers were selected (Supplementary Fig. 