Microchimerism in sensitized renal patients

Patients exposed to allogeneic human tissue sometimes produce anti-HLA antibody for many years in the absence of further obvious antigen exposure. To investigate the mechanism of sustained sensitization, we identified females awaiting renal transplantation with high panel-reactive antibody but no exposure to allogeneic tissue for at least 1 month.

We analyzed peripheral blood microchimerism using nested polymerase chain reaction amplification specific for the SRY region of the Y chromosome.

Microchimerism was detected in 3 of 10 patients but in none of 8 normal female subjects. In two cases, the amplified DNA polymerase chain reaction product was sequenced and was confirmed to be identical to the SRY gene. The estimated level of chimerism as compared with serial dilutions of DNA from male peripheral blood leukocytes was about 1/50000.

These results do not establish causality but support the possibility that antigens from microchimeric donor cells may sustain the HLA antibody response in certain patients.