Week 8-9 Blood Groups PDF

OTHER MAJOR 8-9 BLOOD GROUPS LEWIS (007) SYSTEM Lewis gene (Le) codes for the production of fucosyltransferase enzyme 1. Lewis Antigens Erythrocytes acquire the Lewis phenotype by adsorbing Lewis substances from the plasma, rather than being membrane-bound antigens The Lewis antigen is not true bloo...

OTHER MAJOR 8-9 BLOOD GROUPS LEWIS (007) SYSTEM Lewis gene (Le) codes for the production of fucosyltransferase enzyme 1. Lewis Antigens Erythrocytes acquire the Lewis phenotype by adsorbing Lewis substances from the plasma, rather than being membrane-bound antigens The Lewis antigen is not true blood group antigen The Lewis antigens differ from all other blood groups in that it is soluble and found in plasma and saliva Lewis antigens found in the secretions are glycoproteins Lewis antigens found in plasma are glycolipids The Leb antigen is the receptor for Helicobacter pylori, a gram-negative bacterium associated with gastritis, peptic ulcer disease, gastric carcinoma, and the Norwalk virus Le adsorption Le Expression is influenced by the presence of: 1. Se gene Determines the secretor status Produces the ability to secrete water-soluble blood group-specific substances 2. H gene Produces the ability to secrete H antigen Inherited by means of 2 genes: 1. Lewis positive gene (Le) converts the precursor material to Lea substance 2. Lewis negative gene (le) cannot convert the precursor material to Le substance Rules regarding Le antigen expression: 1. lele individual will not produce any antigen lele ---> Le (a-b-) 2. A person with at least one Le gene and sese genes will be Lele/Lele and sese ---> Le (a+b-) 3. A person who inherits at least one Le gene and at least one Se gene will be Leb positive: Lele/Lele and Sese/Sese ---> Le (a-b+) Le precursor Substance Le gene Lea Se gene Leb Genotype Substance red cell phenotype ABO Secretor Lewis ABH sese lele ABH lele ABH LeLe/Lele ABH ABH SeSe/Sese LeLe/Lele ABH ABH SeSe/Sese ABH sese ABO/Se LEWIS Le Antibodies 2. Lewis antibodies Considered naturally occurring; igM in nature Activate the complement and can cause in vivo and in vitro hemolysis Hemolysis is sometimes seen in vitro, especially if fresh serum is used, because antiLea efficiently binds complement Neutralization techniques using commercially prepared Lewis substance may be helpful to confirm the presence of a Lewis antibody or eliminate the reactions to identify other antibodies mixed in the serum Lewis System Phenotypes and Frequencies: Reaction with Interpretation Frequency (%) Anti-Lea Anti-Leb Phenotype Whites Blacks + 0 Le (a+b-) 22 23 0 + Le(a-b+) 72 55 0 0 Le(a-b-) 6 22 + + Le(a+b+) Rare Rare MNSsU (002) BLOOD GROUP SYSTEM The MNSs system demonstrates dosage effect MN sialoglycoprotein (MN-SGP) 1. MN Antigens Found on glycophorin A MN antigens differ in their amino acid residues at positions 1 and 5 M has serine (at position 1) and glycine (at position S) N has leucine (at position 1) and glutamate (at position S) Well developed at birth: M and N are codominant alleles in paternity testing Easily destroyed or removed by enzymes 2. Ss Antigens Located on glycophorin B Amino acid at position 29 is critical to antigen expression S has methione whereas s has threonine Well developed at birth Less easily degraded by enzymes variable effect from ficin treatment 3. U Antigen located near the membrane and is always present when S or s is inherited; resistant to ficin 3. Anti-M Most examples are naturally occurring cold-reactive saline agglutinins IgM or IgG; usually do NOT bind the complement Do not react with enzyme-treated red cells Some examples are pH-dependent, reacting best at ph 6.5 Other examples react only with red cells exposed to glucose solutions Rarely causes HTR + enzyme =