Alloantibodies to a paternally derived RBC KEL antigen lead to hemolytic disease of the fetus/newborn in a murine model

Abstract

• Anti-KEL alloantibodies generated after exposure to paternally derived RBC antigens during pregnancy result in fetal anemia.• This is the first animal model of pregnancy associated HDFN, with transfusion and pregnancy resulting in boostable anti-KEL alloantibodies.Exposure to nonself red blood cell (RBC) antigens, either from transfusion or pregnancy, may result in alloimmunization and incompatible RBC clearance. First described as a pregnancy complication 80 years ago, hemolytic disease of the fetus and newborn (HDFN) is caused by alloimmunization to paternally derived RBC antigens. Despite the morbidity/mortality of HDFN, women at risk for RBC alloimmunization have few therapeutic options. Given that alloantibodies to antigens in the KEL family are among the most clinically significant, we developed a murine model with RBC-specific expression of the human KEL antigen to evaluate the impact of maternal/fetal KEL incompatibility. After exposure to fetal KEL RBCs during successive pregnancies with KEL-positive males, 21 of 21 wild-type female mice developed anti-KEL alloantibodies; intrauterine fetal anemia and/or demise occurred in a subset of KEL-positive pups born to wild type, but not agammaglobulinemic mothers. Similar to previous observations in humans, pregnancy-associated alloantibodies were detrimental in a transfusion setting, and transfusion-associated alloantibodies were detrimental in a pregnancy setting. This is the first pregnancy-associated HDFN model described to date, which will serve as a platform to develop targeted therapies to prevent and/or mitigate the dangers of RBC alloantibodies to fetuses and newborns. (Blood. 2013;122(8):1494-1504

Antigen Modulation Confers Protection to Red Blood Cells from Antibody through Fcγ Receptor Ligation

“…Blood collected was washed with PBS and labeled with one of three different lipophilic dyes used to track the survival of these RBCs posttransfusion, as outlined previously (29,30). Briefly, HOD blood was typically labeled with 1,19-dioctadecyl-3,3,3939-tetramethylindocarbocyanine perchlorate (DiI), and FVB blood was typically labeled with 3,39-dihexadecyloxacarbocyanine perchlorate (DiO).…”

Novel methods for studying normal and disordered erythropoiesis

“…This novel method not only enables successful in vivo quantitation of murine terminal erythroid differentiation, but also could clearly separate all murine terminally differentiating erythroid cells: Pro, Baso, Poly, Ortho erythroblasts, reticulocytes, and red blood cells. This novel method provided accurate means for studying erythroid differentiation and erythroid related disorders in mouse model [40][41][42][43][44]. Evaluating this achievement in a review, professor Palis said: this research created a novel method of realizing the separation of cell subsets through flow cytometry and the obtained cells can be used in the further research [45].…”

Factors Influencing RBC Alloimmunization: Lessons Learned from Murine Models

“…In contrast, monoclonal antibodies against the hGPA antigen are clinically significant, in that they lead to hemolytic transfusion reactions [66,67] through a complement- and Fcγ receptor-independent process [68,69]. Polyclonal antibodies against the KEL2 antigen are clinically significant in both transfusion and pregnancy scenarios: hemolytic transfusion reactions are mediated by both complement and Fcγ receptors [70], while hemolytic disease of the fetus and newborn appears to be due at least in part to suppression of erythropoiesis by anti-KEL glycoprotein alloantibodies [71]. …”

“…In the KEL2 murine model, anti-KEL glycoprotein alloantibodies develop not only following transfusion of KEL2 RBCs into C57BL/6 mice [97] but also after pregnancy in C57BL/6 female mice bred with KEL2 transgenic males [71]. The titers of anti-KEL glycoprotein immunoglobulins increase with repeat antigen exposure, whether the exposure is due to multiple RBC transfusions or due to multiple pregnancies/deliveries [71,97]. All IgG subtypes are generated in response to KEL2 RBC exposure by both pregnancy and transfusion, with these antibodies being clinically significant in both settings.…”