Kidney Transplant vs Blood Type

FIGHT!!

Overview

ABO• Antigen is expressed on RBCs, lymphocytes, and platelets, as well as epithelial and

endothelial cells.• Formation of blood group antibodies occurs against those antigens not native to the host. • Types A and O most frequently found in the US population

– Given the distribution of blood group antigens in the US, the waiting time on the deceased donor allograft (DDA) list is prolonged for patients with blood group B or O

• Blood group A consists of two subtypes, A1 and A2. Approximately 80 percent of individuals in the US with blood group A express A1– The antigenic expression of A2 is quantitatively and qualitatively less than that of A1 and the

overall immunogenic risk based on antigen expression alone is A1>B>A2– Given the lower immunogenic risk of the A2 antigen, donor A2 kidneys can generally be

successfully transplanted into recipients with low pretransplant anti-A titers without the use of desensitization

• Type O individuals tend to have higher isoagglutinin antibody titers to both the A and B antigen, as compared to the formation of anti-B by blood group A individuals or anti-A by blood group B individuals. – Type O recipients have a higher incidence of antibody mediated rejection (AMR) following ABO

Incompatible transplantation

ABO desensitization

• Two methods used to reduce circulating ABO antibody titers are plasmapheresis and immunoabsorption– Plasmapheresis = removal of the plasma that contains

ABO antibodies and administration of a medication to prevent their production

– Immunoadsorption not yet approved in USA– Goal is to achieve titers of ≤1:8 to 1:32

• Splenectomy, IVIg, and rituximab have been used as adjunctive therapies

Rh Factor• The Rh antigen does not function as a "transplantation antigen,"

because it is only present on the surface of red blood cells and not on the parenchymal cells of the graft

• Rh-mismatched transplanted organs are not rejected more frequently than Rh-matched organs

• “Passenger lymphocyte" syndrome– Rh-negative donor who has been previously sensitized gets matched with

an Rh-positive recipient– The memory B lymphocytes and plasma cells that are transplanted with

the organ can be stimulated to produce anti-Rh antibody– Causes short-lived hemolytic anemia in the recipient. Hemolysis can last up

to 6 months after transplantation in some cases– Hemolysis can generally be managed by transfusion with Rh-negative RBCs

References

• http://www.medscape.com/viewarticle/414309

• http://www.intechopen.com/books/understanding-the-complexities-of-kidney-transplantation/abo-incompatible-kidney-transplantation

• http://www.kidney.org/transplantation/livingdonors/incompatiblebloodtype.cfm