Immune responses to red blood cell antigens

The research described in this thesis is aimed towards elucidation of the mechanism of action of anti-D. Anti-D is administered prophylactivly to prevent alloimmunization against the immunogenic D-antigen to D⁻ pregnant women carrying a D⁺ fetus. The plasma of women who became immunized during pregnancy, is pooled to create anti-D. The prophylactic administration of anti-D is one of the most successful clinical applications of antibody mediated immune suppression. As a result of this success, less women become immunized and it becomes increasingly difficult to recruit sufficient numbers of anti-D donors. To circumvent this problem a donor independent recombinant/monoclonal antibody would be preferred. Production of suitable monoclonal/recombinant antibodies is impaired because the mechanism of action remains unknown. Elucidation of this mechanism of action in turn, is complicated because suitable experimental models are not available. In this thesis we aimed to create a suitable experimental model by investigated which additional proteins are required for stable RhD expression on an erythroblast cell line. Furthermore, we characterized RhD variants found in D-negative women to predict their immunization risk. Using human and animal experimental models we discovered that, contrary to what is often assumed, there appears to be no relationship between red blood cell clearance and immune response. We found that the immune response is heavily dependent on IgG subclass and IgG fucosylation level. Additionally, we describe a novel technique of measuring IgG and FcγR avidity levels using opsonized red blood cells. The role of FCGR-polymorphisms in developing red blood cell alloantibodies is also discussed.