The long-term goal of this project is to determine which individuals are at greatest risk of developing
clinically meaningful alloantibodies to platelet transfusion, and why, to enable targeted interventions to reduce
these risks. Alloimmunization targeting donor MHC antigens is a common consequence of platelet transfusion
and can cause serious harm including rejection of future transfusions or transplants. Measurements of the
incidence of anti-MHC antibodies in platelet recipients vary widely, ranging from 7-55%. Many factors can
influence alloimmunization outcomes, but one less studied area is the influence of the recipient's underlying
health. The majority of the illnesses and medical interventions that necessitate transfusion have a profound
impact on the immunological environment in which transfused donor antigens are encountered. Efforts to
evaluate the role of patient health on alloimmunization have been limited as different groups of patients are
treated with varying types and amounts of blood products.
Here we propose to determine how different forms of immune modulation, common among transfusion
recipients, influence the alloresponse to foreign MHC. An established murine model of transfusion-induced
alloimmunization to MHC will be used to isolate the role of recipient health under controlled and standardized
conditions. The central hypothesis is that the immunological environment established by the health of the
recipient has a strong impact on both the magnitude and quality of the anti-MHC antibody response to
allogeneic transfusion, driven by differences in B cell differentiation and T cell help. The specific aims are to
evaluate the impact of inflammation or immunosuppressive therapies at the time of allogeneic transfusion on 1)
alloantibody responses to MHC antigens, activation of allospecific B cells and the development of durable
immunity; 2) the immunological environment and the quality of T cell help; and 3) the clinical significance and
functional capabilities of alloantibodies generated under these different inflammatory or suppressive conditions.
Three model interventions are included: chemotherapy (cancer treatment), LPS (bacterial infection), and
poly(I:C) (viral infection). Antibodies against class I and class II MHC will be measured by isotype over time
using our established assays. Through the use of MHC-tetramers, rare endogenous MHC-specific B cell
populations will be examined in wild-type (non-transgenic/knock-out) mice under defined physiological
conditions. Impact on cytokine milieu, T cell differentiation, and lymphocyte homeostasis will be determined.
The clinical significance of alloantibodies will be assessed by their ability to drive rejection in models of platelet
refractoriness and bone marrow transplantation. This work will identify classes of transfusion recipients at
greatest risk for development of clinically meaningful anti-MHC antibodies, and the mechanisms driving these
responses, which will inform future transfusion practice and development of new therapeutics.