Although RBC transfusion can result in the development of anti-RBC alloantibodies that increase the probability of life-threatening hemolytic transfusion reactions, not all patients generate anti-RBC alloantibodies. However, the factors that regulate immune responsiveness to RBC transfusion remain incompletely understood. One variable that may influence alloantibody formation is RBC alloantigen density. RBC alloantigens exist at different densities on the RBC surface and likewise exhibit distinct propensities to induce RBC alloantibody formation. However, although distinct alloantigens reside on the RBC surface at different levels, most alloantigens also represent completely different structures, making it difficult to separate the potential impact of differences in Ag density from other alloantigen features that may also influence RBC alloimmunization. To address this, we generated RBCs that stably express the same Ag at different levels. Although exposure to RBCs with higher Ag levels induces a robust Ab response, RBCs bearing low Ag levels fail to induce RBC alloantibodies. However, exposure to low Ag–density RBCs is not without consequence, because recipients subsequently develop Ag-specific tolerance. Low Ag–density RBC–induced tolerance protects higher Ag–density RBCs from immune-mediated clearance, is Ag specific, and occurs through the induction of B cell unresponsiveness. These results demonstrate that Ag density can potently impact immune outcomes following RBC transfusion and suggest that RBCs with altered Ag levels may provide a unique tool to induce Ag-specific tolerance.
This work was supported in part by the Burroughs Wellcome Trust Career Award for Medical Scientists and National Institutes of Health Early Independence Grant DP5OD019892 (to S.R.S.).
The online version of this article contains supplemental material.
Abbreviations used in this article:
- regulatory B cell
- hen egg lysozyme
- hen egg lysozyme, OVA fused to Duffy
- human Kell
- KELlo RBC
- RBC expressing low levels of KEL
- KEL RBC
- RBC expressing high levels of KEL
- mean fluorescence intensity
- polyinosinic-polycytidylic acid
- regulatory T cell.
- Received October 11, 2016.
- Accepted January 15, 2017.
- Copyright © 2017 by The American Association of Immunologists, Inc.