DUFFY AND LEWIS BLOOD GROUP SYSTEM Flashcards
Explain the role of Duffy antigens in malaria and how this relates to transfusion risks
Duffy antigens (Fy (a) and Fy (b)) act as receptors for the malaria parasite Plasmodium vivax. Individuals who lack these antigens (Fy(a-b-)) are resistant to infection by this parasite. However, in transfusion medicine, the presence of anti-Duffy antibodies can cause hemolytic transfusion reactions (HTRs), particularly in patients who have been sensitized through previous transfusions or pregnancies.
How do the expression of Lewis antigens Le (a) and Le (b) depend on the interaction of Le and Se genes, and what implications does this have for transfusion reactions?
The expression of Lewis antigens depends on both the Le and Se (Secretor) genes. Individuals who are Le (a-b-) lack Lewis antigens entirely, while those who are Le (a+b-) express Le (a) and those who are Le (a-b+) express Le (b). This genetic variation impacts the presence of Lewis antibodies. In transfusion scenarios, mismatched Lewis antigens can occasionally lead to mild hemolytic reactions, particularly in individuals with a high titer of Lewis antibodies
Why are Lewis antibodies usually not considered clinically significant, and in what scenarios might they still pose a risk?
Lewis antibodies (anti-Le (a) and anti-Le (b)) are typically not considered clinically significant because Lewis antigens are not firmly fixed on red blood cells; they can be adsorbed and eluted. Thus, they rarely cause severe hemolytic reactions. However, in rare cases, such as in patients with compromised immune systems or those with multiple transfusions, these antibodies might cause mild hemolytic transfusion reactions.
Discuss the mechanism by which Duffy antibodies can lead to hemolytic transfusion reactions (HTRs).
Duffy antibodies, such as anti-Fy (a) and anti-Fy (b), can lead to hemolytic transfusion reactions by binding to the corresponding Duffy antigens on transfused red blood cells. This binding triggers the immune system to recognize and destroy the transfused cells, leading to hemolysis. Symptoms can include fever, chills, and hemoglobinuria. This is particularly a concern in patients with sickle cell disease who may have been previously sensitized
Why is it essential to consider the presence of anti-Duffy antibodies in patients with sickle cell disease undergoing transfusion?
Patients with sickle cell disease often receive multiple transfusions, which increases their risk of developing antibodies against minor blood group antigens, including Duffy antigens. The presence of anti-Duffy antibodies can cause hemolytic transfusion reactions, which can be particularly severe and complicate the management of these patients. Therefore, it’s crucial to screen for and match these antibodies to prevent transfusion reactions.
Describe the clinical significance of anti-Fy (a) antibodies in transfusion medicine
Anti-Fy (a) antibodies are clinically significant because they can cause acute hemolytic transfusion reactions (HTRs). These antibodies can bind to Fy (a) antigens on transfused red blood cells, leading to their destruction and potentially severe symptoms like fever, chills, and hemoglobinuria.
How do the antigenic properties of Lewis antigens influence the formation of Lewis antibodies?
Lewis antigens, being adsorbed onto red blood cells and present in body fluids, can vary with changes in the individual’s secretor status and the Le gene. This variability influences the formation of Lewis antibodies, as exposure to different antigen forms can stimulate an immune response, leading to the production of anti-Le (a) or anti-Le (b) antibodies
Explain why Lewis antibodies (anti-Le (a) and anti-Le (b)) are typically not associated with hemolytic disease of the newborn (HDN).
Lewis antibodies are typically not associated with HDN because Lewis antigens are not well developed on fetal red blood cells. Additionally, Lewis antigens are primarily adsorbed onto the red blood cell surface rather than being integral membrane proteins, reducing the likelihood of significant antibody-mediated hemolysis in newborns.
What is the genetic basis for the absence of Duffy antigens in some populations, and how does this impact transfusion practices?
In some populations, particularly in West Africa, the absence of Duffy antigens (Fy(a-b-)) is due to a genetic mutation that prevents the expression of Fy (a) and Fy (b) antigens on red blood cells. This provides resistance to Plasmodium vivax malaria. In transfusion practices, individuals without Duffy antigens do not produce anti-Fy antibodies, reducing the risk of HTRs from these antigens.
Discuss the potential complications of transfusions involving patients with high-titer Lewis antibodies.
Although rare, high-titer Lewis antibodies can cause hemolytic transfusion reactions (HTRs). Complications may include mild to moderate hemolysis, leading to symptoms such as jaundice and anemia. Transfusions should be carefully managed by selecting donor blood that minimizes the risk of reactions, and crossmatching tests should be conducted to ensure compatibility.
