RecruitingStudy to Understand the Genetic Risk of Developing an Immune Response After Blood Transfusions Among Individuals With Sickle Cell DiseaseThe purpose of this research study is to look at genes and determine how they interact with each other to find changes that could explain why some people's immune systems may respond to blood transfusions. This response is called an alloimmune response. We strongly believe that when someone has an alloimmune response, it is caused by changes in their genes. We plan to compare changes in the genes of individuals that develop red blood cell alloimmunization after blood transfusions with those that do not develop alloimmunization. This may help us to create more targeted therapeutic interventions, which may improve the health of alloimmune responders.