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IMPORTANCE OF DETERMINING Cw LOCUS ON IDENTICAL SIBLINGS FOR STEM CELL TRANSPLANTATION.
Luz A. Stamm, BSc, MLT , Charlene Ott MLT , Irene Shewchuk MLT , Iwona Galaskiewicz ART , Elizabeth Potok MLT , Leona Kowalick MLT and Jane Hickerty MLT . Calgary AB, Canada, Calgary Laboratory Services, FMC Site, T2N 2T9, Tissue Typing Laboratory .

The importance of using HLA-matched donors for allogeneic stem cell transplantation is critical for the outcome of the patient. As reported by the NMDP, a single mismatch at the HLA A, B, or C locus leads to a higher incidence of Grade III and IV acute GVHD and increased mortality. In early disease stages, a single mismatched antigen in a related sibling will have an impact on the transplant success (Journal of Clinical Oncology, 1997).
HLA investigation in our laboratory on identical siblings of recipients requiring stem cell allogeneic transplants is done by serological methods and PCR – Reverse SSOP. Lymphocytes are separated using bead separation (One Lambda) and serological testing is performed using two different typing trays (Terasaki, GTI). Class II DR-DQ typing is carried out by Reverse SSOP using the Dynal Method.
An AML recipient and seven siblings were typed by this Laboratory. Three siblings appeared identical by HLA A and B serology. One sibling had a Cw2 serological reactivity. Class II testing by Reverse SSOP showed the three siblings to be identical. Cw by Reverse SSOP was done on the three siblings and revealed a mismatch in one of them. The haplotypes determined on this patient are as follows:

HLA Haplotypes
HaplotypeABCwDRB1DQB1
115706XX03XX02XX
226112XX11XX03XX
326003XX
426102XX11XX03XX


As a result of this case, we have instituted a new policy in our laboratory that includes testing for intermediate resolution of HLA-Cw locus for all patients and identical siblings for allogeneic stem cell transplantation.