Sickle cell disease (SCD) is a chronic genetic blood disorder inherited from both parents. Having sickle cell trait (inheriting the gene from one parent but not the other) is an advantage against malaria, which is why SCD primarily impacts people of African, Mediterranean, Middle Eastern, and Indian descent.
But the disease itself (which happens when someone inherits genes from both parents) is devastating.
When someone has SCD, their red blood cells are shaped like stiff crescents instead of flexible discs. These pointed cells can snag on blood vessel walls, causing blockages that prevent oxygen from reaching tissues, incredible pain (called a crisis), and damage to a patient’s brain, eyes, internal organs, joints, bones, and skin. These complications can be life-threatening.
Approximately 1 in 500 African Americans (100,000 people in the U.S) have SCD, though as many as 1 in 13 African Americans are carriers of sickle cell trait.
Treatment of SCD often includes chronic blood transfusion therapy to increase the number of healthy red blood cells in the bloodstream, even when a patient is not actively sick. Transfusions can reduce the chance of stroke.
Says Bloodworks Research Institute’s Dr. James Zimring,
The more we study the disease, the more we understand that transfusions are needed earlier and more frequently than we have appreciated.
Anyone who receives regular blood transfusions is at risk of developing antibodies against antigens in other people’s blood, called alloimmunization. The more antibodies someone makes, the harder it becomes to find blood they can still receive.
Transfusion for transfusion, patients with SCD are more likely to develop antibodies than someone without it. Although science is working hard on it, no one understands all of the reasons why.
Most of us know that our blood type is either A, B, O or AB, and Rh positive or negative, which correspond to antigens on the red cells, but there are actually hundreds of other antigens in the blood.
When sickle cell pediatric patients get transfusions from our blood bank. they require specially matched red cells. Most patients receive blood that’s matched for ABO and Rh,
Other than matching blood to patients, there is no way to prevent a reaction besides not transfusing. For some patients, this can to lead delays, substandard care, and even death.
BloodworksNW’s Immunohematology & Red Blood Cell Genomics Reference Laboratory performs the extended blood typing and matching for patients in the community. Sickle cell patients also have blood typing done by genotype, or molecular methods, since there tends to be blood group differences in people of different ethnic backgrounds that can make figuring different blood types more complicated.
Dr. Zimring explains:
Antigens tend to be within an ethnic group. You are more likely to be a match to someone who has a similar ancestry as you do. Therefore, the more people who have a similar ancestry that donate blood, the more likely it is that compatible blood will be available.
Dr. Zimring hopes to uncover why SCD patients are so difficult to transfuse. He and BloodworksNW’s Dr. Krystalyn Hudson are studying the process by which the immune system makes antibodies to transfused red blood cells.
Understanding why sickle cell patients make antibodies at a greater frequency might help scientists understand why any patient might make an antibody.
This awareness will help researchers formulate new therapeutic approaches, which will help both sickle cell patients and others receiving regular transfusions.
One thing is for certain:
Sickle cell disease would benefit from increased resources for delivery of medical care and research.