Welcome Back to Immunohematology

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Welcome Back to Immunohematology
Other Antigen SystemsPart III Lewis, P,
Lutheran, Xg, I
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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.

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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.

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Lewis System

• Naturally occurring?
• HTR?
• HDFN?
• Clinically significant?

• Yes
• No
• No
• No

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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.

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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

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P System

• Naturally occurring?
• HTR?
• HDFN?
• Clinically significant?

• Yes
• No
• No
• No

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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.

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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.

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Lutheran System

• Naturally occurring?
• HTR?
• HDFN?
• Clinically significant?

• Lua yes
• Lub no
• Lub may
• Lua no
• Lub may
• Lua no
• Lub yes
• Lua no

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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.

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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

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I and i

• Naturally occurring?
• HTR?
• HDFN?
• Clinically significant?

• Yes
• No
• No
• No

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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.

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Xg System

• Naturally occurring?
• HTR?
• HDFN?
• Clinically significant?

• No
• No
• No
• No