Transfusion-related acute lung injury-associated HNA-3a antibodies recognize complex determinants on choline transporter-like protein 2.
BACKGROUND
HNA-3a-specific antibodies can cause severe, sometimes fatal, transfusion-related acute lung injury when present in transfused blood. The HNA3-a/b antigens are determined by an R154Q polymorphism in the first of five extracellular (EC) loops of the 10-membrane-spanning choline transporter-like protein 2 (CTL2) expressed on neutrophils, lymphocytes, and other tissues. Approximately 50% of HNA-3a antibodies (Type 1) can be detected using CTL2 Loop 1 peptides containing R154; the remaining 50% (Type 2) fail to recognize this target. Understanding the basis for this difference could guide efforts to develop practical assays to screen blood donors for HNA-3 antibodies.


METHODS
Reactions of HNA-3a antibodies against recombinant versions of human, mouse, and human/mouse (chimeric) CTL2 were characterized using flow cytometry and various solid-phase assays.


RESULTS
The findings show that, for binding to CTL2, Type 2 HNA-3a antibodies require nonpolymorphic amino acid residues in the third, and possibly the second, EC loops of CTL2 to be in a configuration comparable to that found naturally in the cell membrane. In contrast, Type 1 antibodies require only peptides from the first EC loop that contain R154 for recognition.


CONCLUSIONS
Although Type 1 HNA-3a antibodies can readily be detected in solid-phase assays that use a CTL2 peptide containing R154 as a target, development of a practical test to screen blood donors for Type 2 antibodies will pose a serious technical challenge because of the complex nature of the epitope(s) recognized by this antibody subgroup.
Blood Research Institute, BloodCenter of Wisconsin, Milwaukee, Wisconsin.
Daniel W
DW
Bougie
Julie A
JA
Peterson
Adam J
AJ
Kanack
Brian R
BR
Curtis
Richard H
RH
Aster
D055371:Acute Lung Injury / Q000139:chemically induced / Q000235:genetics / Q000276:immunology*; D000818:Animals; D001323:Autoantibodies / Q000276:immunology* / Q000633:toxicity; D001782:Blood Donors; D001803:Blood Transfusion; D004195:Disease Models, Animal; D046148:Donor Selection / Q000379:methods; D005260:Female; D057809:HEK293 Cells; D006801:Humans; D007519:Isoantigens / Q000235:genetics / Q000276:immunology*; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics / Q000276:immunology*; D026901:Membrane Transport Proteins / Q000235:genetics / Q000276:immunology*; D051379:Mice; D017433:Protein Structure, Secondary; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000276:immunology
D001323:Autoantibodies; C518134:HNA-3a antigen, human; D007519:Isoantigens; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D011993:Recombinant Fusion Proteins; C484524:SLC44A2 protein, human; C571060:SLC44A2 protein, mouse