Welcome Back to Immunohematology Other Antigen Systems Part III – Lewis, P, Lutheran, Xg, I

Lewis System  Primary antigens are Le a and Le b.  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 37 o C and AHG phases.  Agglutinates may be fragile.  Do not show dosage.  May activate complement.  Anti- Le a is known for causing hemolysis at 37 o C.

Lewis System  Naturally occurring?  HTR?  HDFN?  Clinically significant?  Yes  No

P System  The antigens of the P system are:  P  P 1  P k  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-P 1 is a common cold agglutinin  Reacts best at o C or colder  Usually IgM  Anti-P may act as a biphasic hemolysin  Do not show dosage

P System  Naturally occurring?  HTR?  HDFN?  Clinically significant?  Yes  No

Lutheran System  Alleles are Lu a and Lu b.  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- Lu a  Naturally occurring  Usually IgM, but may be IgG or IgA  Reacts best at room temperature or colder  Anti- Lu b  Immune  Most often IgG  Reacts best at 37 o C and AHG  Show dosage.  May activate compliment.

Lutheran System  Naturally occurring?  HTR?  HDFN?  Clinically significant?  Lu a yes  Lu b no  Lu b may  Lu a no  Lu b may  Lu a no  Lu b yes  Lu a 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?  HTR?  HDFN?  Clinically significant?  Yes  No

Xg System  Only one allele – Xg a.  Sex linked gene –X chromosome.  89% of females and 66% of males are Xg a positive.  Destroyed by enzymes.  Rare IgG antibody that reacts at AHG phase.

Xg System  Naturally occurring?  HTR?  HDFN?  Clinically significant?  No