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Chapter 107. Transfusion Biology and Therapy (Part 3)

The MNSsU system is regulated by genes on chromosome 4. M and N are determinants on glycophorin A, an RBC membrane protein, and S and s are determinants on glycophorin B. Anti-S and anti-s IgG antibodies may develop after pregnancy or transfusion and lead to hemolysis. Anti-U antibodies are rare but problematic; virtually every donor is incompatible because nearly all persons express U. The Kell protein is very large (720 amino acids), and its secondary structure contains many different antigenic epitopes. The immunogenicity of Kell is third behind the ABO and Rh systems. The absence of the Kell precursor protein. | Chapter 107. Transfusion Biology and Therapy Part 3 The MNSsU system is regulated by genes on chromosome 4. M and N are determinants on glycophorin A an RBC membrane protein and S and s are determinants on glycophorin B. Anti-S and anti-s IgG antibodies may develop after pregnancy or transfusion and lead to hemolysis. Anti-U antibodies are rare but problematic virtually every donor is incompatible because nearly all persons express U. The Kell protein is very large 720 amino acids and its secondary structure contains many different antigenic epitopes. The immunogenicity of Kell is third behind the ABO and Rh systems. The absence of the Kell precursor protein controlled by a gene on X is associated with acanthocytosis shortened RBC survival and a progressive form of muscular dystrophy that includes cardiac defects. This rare condition is called the McLeod phenotype. The Kx gene is linked to the 91-kDa component of the NADPH-oxidase on the X chromosome deletion or mutation of which accounts for about 60 of cases of chronic granulomatous disease. The Duffy antigens are codominant alleles Fya and Fyb that also serve as receptors for Plasmodium vivax. More than 70 of persons in malaria-endemic areas lack these antigens probably from selective influences of the infection on the population. The Kidd antigens Jka and Jkb may elicit antibodies transiently. A delayed hemolytic transfusion reaction that occurs with blood tested as compatible is often related to delayed appearance of anti-Jka. Pretransfusion Testing Pretransfusion testing of a potential recipient consists of the type and screen. The forward type determines the ABO and Rh phenotype of the recipient s RBC by using antisera directed against the A B and D antigens. The reverse type detects isoagglutinins in the patient s serum and should correlate with the ABO phenotype or forward type. The alloantibody screen identifies antibodies directed against other RBC antigens. The alloantibody screen is performed by mixing