Christoffer Dellgren

Cell surface expression level variation between two common Human Leukocyte Antigen alleles, HLA-A2 and HLA-B8, is dependent on the structure of the C terminal part of the alpha 2 and the alpha 3 domains

Constitutive cell surface expression of Human Leukocyte Antigen (HLA) class I antigens vary extremely from tissue to tissue and individual antigens may differ widely in expression levels. Down-regulation of class I expression is a known immune evasive mechanism used by cancer cells and viruses. Moreover, recent observations suggest that even minor differences in expression levels may influence the course of viral infections and the frequency of complications to stem cell transplantation. We have shown that some human multipotent stem cells have high expression of HLA-A while HLA-B is only weakly expressed, and demonstrate here that this is also the case for the human embryonic kidney cell line HEK293T. Using quantitative flow cytometry and quantitative polymerase chain reaction we found expression levels of endogenous HLA-A3 (median 71,204 molecules per cell) 9.2-fold higher than the expression of-B7 (P = 0.002). Transfection experiments with full-length HLA-A2 and -B8 encoding plasmids confirmed this (54,031 molecules per cell vs. 2,466, respectively, P = 0.001) independently of transcript levels suggesting a post-transcriptional regulation. Using chimeric constructs we found that the cytoplasmic tail and the transmembrane region had no impact on the differential cell surface expression. In contrast, ~65% of the difference could be mapped to the six C-terminal amino acids of the alpha 2 domain and the alpha 3 domain (amino acids 176–284), i.e. amino acids not previously shown to be of importance for differential expression levels of HLA class I molecules. We suggest that the differential cell surface expression of two common HLA-A and–B alleles is regulated by a post-translational mechanism that may involve hitherto unrecognized molecules.

The use of next-generation sequencing for the determination of rare blood group genotypes

Next‐generation sequencing (NGS) for the determination of rare blood group genotypes was tested in 72 individuals from different ethnicities.

Results of noninvasive prenatal RHD testing in Gestation Week 25 are not affected by maternal body mass index: NIP RHD IS NOT AFFECTED BY MATERNAL BMI

Reliability of noninvasive prenatal RHD genotype test (NIP RHD) depends on having sufficient amounts of cell‐free fetal DNA (cffDNA) in the maternal plasma sample. The fraction of cffDNA in maternal plasma is inversely related to maternal body mass index (BMI), suggesting that high maternal BMI may limit the tests accuracy. This study determined the effect of maternal BMI on the accuracy of NIP RHD.

Using Blood Donor-Derived ABO and RhD Blood Groups Helps to Detect Wrong Blood in Tube Errors in Recipients

Background: Comparing the ABO and RhD group of a recipients current pre-transfusion sample against their historical group is an important means of detecting wrong blood in tube (WBIT) errors. This study investigated the utility of using the donor ABO and RhD group as the historical check for recipients. Methods: A single database stores serological information on blood donors, pregnant women, and patients throughout southern Denmark. A donor ABO and RhD group can be the historical blood group should that donor later require a transfusion. This database was searched to determine how often the ABO and RhD group on a recipients current pre-transfusion sample was discrepant with their historical donor-derived blood group. Results: During about 21 years, ABO and RhD groupings were performed on 76,455 blood donors and on 424,697 patients. There were 13,630/424,697 (3.2%) patients who had their donor-derived ABO and RhD group used as the historical comparison with the current sample; 6/13,630 (0.04%) of the current pre-transfusion samples on these patients were discrepant with the donor-derived historical group because of WBIT errors. Seven other discrepancies with the donor-derived blood group were also found. Conclusion: Accessing the donor-derived ABO and RhD group can be an important safeguard against WBIT-mediated mistransfusions.

Low Constitutive Cell Surface Expression of HLA-B Is Caused by a Posttranslational Mechanism Involving Glu180 and Arg239

HLA class I cell surface expression is crucial for normal immune responses, and variability in HLA expression may influence the course of infections. We have previously shown that classical HLA class I expression on many human cell types is biased with greatly reduced expression of HLA-B compared with HLA-A in the absence of inflammatory signals. In the search for the mechanisms responsible for this discrepancy, we have recently reported that the regulation is mainly posttranslational and that the C-terminal part of the α2 domain and the α3 domain contain the molecular determinants that explain most of the variability of expression between common HLA-A and -B allomorphs. In this study, we present a fine mapping of the structural determinants that allow such variability by exchanging key amino acids located within the C-terminal part of the α2 domain and the α3 domain of HLA-A2 and -B8, including Glu/Asp at position 177, Gln/Glu at position 180, Gly/Arg at position 239, and Pro/Ser at position 280. We found that the HLA-A2 and -B8 expression profiles could be interconverted to a large extent by mutual exchange of Gln/Glu at position 180 or by Gly/Arg at position 239. The presence of Gln180 and Gly239, as in HLA-A2, led to higher cell surface expression levels when compared with the presence of Glu180 and Arg239, as in HLA-B8. This indicates that the amino acids at positions 180 and 239 determine the level of cell surface expression of common HLA-A and -B allomorphs, probably by affecting HLA processing in the Ag presentation pathway.