para>Alleles that have been shown not to be expressed, "null " ť alleles, have been given the suffix "N. " ť Based upon regulations required by the American Society of Histocompatibility and Immunogenetics (ASHI) and the National Marrow Donor Program (NMDP), guidelines for null allele typing have been established. The HLA lab is required to test for the following null alleles when alleles and/or haplotypes that have been associated with the specific null alleles exist. Additional CWD null alleles are constantly being updated and incorporated into the required typing list.
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View Large Null Allele Common Related Expressed Type Associated Types Present When Resolution May Be Required A*24:09N A*24:02 B*40 or B*27 B*51:11N B*51:01 A*02, C*15, and DRB1*04 (A*02:01, C*15, and DRB1*04:02) C*04:09N C*04:01 B*44, more specifically, B*44:03 DRB4*01:03N DRB4:01 DRB1*07 and DQB1*03 (DRB1*07:01 and DQB1*03:03) DRB5*01:08N DRB5*01:02 DRB1*15 or, more specifically, DRB1*15:02
Engraftment monitoring (EM) testing - Following HSCT, patients are monitored closely for early engraftment, evidence of graft rejection, or recurrence of the original disease. HSCT creates a donor/recipient chimerism in the patient, which can be quantitatively measured through short tandem repeat (STR) analysis of peripheral whole blood, lineage-specific subsets, whole marrow, or CD34 progenitor cells in the marrow to determine the percent chimerism.
- The pretransplant samples used in the EM assay can be the samples used for HLA typing. No additional pretransplant samples from the patient or the donor are necessary. The most common postsamples are, whole blood, T cells (CD3), B cells (CD19/20), myeloid cells (CD15/CD33/CD66b), NK cells (CD56), whole marrow, and CD34 marrow.
- Results are commonly reported as the percentage of donor chimerism within the post-HSCT samples. The assay sensitivity is a key element and has to be considered in results interpretation and reporting, for example, for a postsample with no patient DNA detected and assay sensitivity is 3%, the result should be reported as more than 97% donor DNA, no patient DNA detected, full engraftment.
Suggested Readings
1Brand ‚ A, Doxiadis ‚ IN, Roelen ‚ DL. On the role of HLA antibodies in hematopoietic stem cell transplantation. Tissue Antigens. 2013;81(1):1 " “11. 2Cooley ‚ S, Weisdorf ‚ DJ, Guethlein ‚ LA Donor selection for natural killer cell receptor genes leads to superior survival after unrelated transplantation for acute myelogenous leukemia. Blood. 2010;116:2411 " “2419. 3Fleischhauer ‚ K, Shaw ‚ BE, Gooley ‚ T Effect of T-cell-epitope matching at HLA-DPB1 in recipients of unrelated-donor haemopoietic-cell transplantation: A retrospective study. Lancet Oncol. 2012;13(4):366 " “374. 4Park ‚ M, Seo ‚ JJ. Role of HLA in hematopoietic stem cell transplantation. Bone Marrow Res. 2012;2012:680841. 5Pegram ‚ HJ, Ritchie ‚ DS, Smyth ‚ MJ Alloreactive natural killer cells in hematopoietic stem cell transplantation. Leuk Res. 2011;35(1):14 " “21. 6Nowak ‚ J. Role of HLA in hematopoietic SCT. Bone Marrow Transplant. 2008;42:S71 " “S76.