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Welcome Back to Immunohematology Other Antigen Systems Part III – Lewis, P, Lutheran, Xg, I Lewis System Primary antigens are Lea and Leb. These are NOT alleles! Antigens are produced in tissues and then adsorbed onto the red cell membrane from the plasma. Antigens are glycolipids on the red cell, but glycoproteins in secretions. The most common Lewis phenotype is Le(a-b+). Enhanced by enzymes. Lewis System Antibodies Very common. Usually IgM. React at immediate spin phase. May also be present at 37oC and AHG phases. Agglutinates may be fragile. Do not show dosage. May activate complement. Anti- Lea is known for causing hemolysis at 37oC. Lewis System Naturally occurring? Yes HTR? No HDFN? No Clinically significant? No P System The antigens of the P system are: P P1 Pk Genes that control expression of these antigens are NOT alleles. Antigens are glycolipids similar to the ABO system. Have variable expression among different people. Enhanced by enzymes. P System Antibodies Anti-P1 is a common cold agglutinin Reacts best at 20-25oC or colder Usually IgM Anti-P may act as a biphasic hemolysin Do not show dosage P System Naturally occurring? Yes HTR? No HDFN? No Clinically significant? No Lutheran System Alleles are Lua and Lub. 92% of Caucasians are Lu(a-b+). Variable antigen expression between individuals. Antigens are glycoproteins. Unaffected by routine enzymes. Lutheran System Antibodies Antibodies to either antigen are uncommon. Anti- Lua Naturally occurring Usually IgM, but may be IgG or IgA Reacts best at room temperature or colder Anti- Lub Immune Most often IgG Reacts best at 37oC and AHG Show dosage. May activate compliment. Lutheran System Naturally occurring? HTR? HDFN? Clinically significant? Lua yes Lub no Lub may Lua no Lub may Lua no Lub yes Lua no I and i I is a high frequency antigen. Carbohydrate structures related to ABH antigens. Born with i; coverts to I by age 18 months. Variable antigen expression. Enhanced by enzymes. I and i Antibodies Cold reacting autoantibodies. Low levels of autoanti-I present in most people. IgM Reacts at room temperature or colder When present in high titers, may result in vascular occlusion or hemolysis Auto anti-i is very rare. Associated with disease processes Do not show dosage May activate complement I and i Naturally occurring? Yes HTR? No HDFN? No Clinically significant? No Xg System Only one allele – Xga. Sex linked gene –X chromosome. 89% of females and 66% of males are Xga positive. Destroyed by enzymes. Rare IgG antibody that reacts at AHG phase. Xg System Naturally occurring? No HTR? No HDFN? No Clinically significant? No