Sharing kidneys across donor-service area boundaries with sensitized candidates can be influenced by HLA C.
The United Network for Organ Sharing (UNOS) implemented the virtual crossmatch system in UNet as a way to improve the likelihood of a negative crossmatch when kidneys are shared with HLA-sensitized candidates across donor service area (DSA) boundaries. The role of HLA C in that process is not universally appreciated. We recently experienced an unexpected positive flow T and B cell crossmatch for an imported, HLA zero-mismatched kidney because of donor-specific HLA C antibodies and transplanted it into the backup candidate. HLA C locus antigens were not typed by the OPO's laboratory that sent the kidney so the UNet virtual crossmatch could not "strike" our candidate from the UNOS match run. HLA C locus typing data of donors for kidneys our DSA imported from other DSAs revealed that C typing was not performed in 23% (14/60) and was discrepant with our molecular type for 10% (6/60) and was concordant in 67% (40/60) of cases. The rate of positive donor-specific crossmatches was higher (83%) for HLA C discrepantly typed donors than for concordantly typed donors (44%). Sensitization for HLA C (42%) is less frequent than for A (80%) or B (83%) locus antigens but the immunogenicity of C locus antigens in patients who make C locus antibodies is equivalent in black and white patients. Finally, the transplant rate of imported kidneys into class I-sensitized candidates was 24%, and C locus-sensitized candidates comprised 55% of those transplanted.
Bryan
Christopher F
CF
HLA Laboratory, Midwest Transplant Network, Westwood, KS, USA. cbryan @mwtn.org
Luger
Alan M
AM
Smith
John L
JL
Warady
Bradley A
BA
Wakefield
Mark
M
Schadde
Erik
E
Murillo
Daniel
D
Nelson
Paul W
PW
D002391:Catchment Area, Health; D050377:Cold Ischemia; D005188:False Negative Reactions; D015236:HLA-C Antigens / Q000502:physiology*; D006650:Histocompatibility Testing; D006801:Humans; D007114:Immunization; D007676:Kidney Failure, Chronic / Q000097:blood / Q000276:immunology* / Q000601:surgery*; D016030:Kidney Transplantation; D009927:Tissue and Organ Procurement / Q000458:organization & administration*
D015236:HLA-C Antigens