IgM Blood Group Systems Flashcards
List the 5 blood groups that are predominantly IgM
Lewis MN (of MNSs) ABO P Ii
List 7 characteristics of IgM antibodies
Large molecule - pentamere
Binds complement efficiently (although agglutination is the most common way to visualize)
Direct agglutinator - Immediate spin reactivity
Room temperature or colder is optimum for sensitization
Often naturally occurring
Do NOT cross the placenta
With the exception of ABO antibodies, IgMs are not clinically significant
What are some characteristics of Lewis antigens?
Found in the saliva and plasma as soluble antigens
They are mfg’d by tissues and released into the body fluids rather than being produced by RBC and incorporated into the membrane
Lewis antigens are adsorbed onto the RBC membrane by never become an integral part
Describe the Lewis gene’s interaction with Se and H
Lewis genes code for fucosyltransferase that adds a fucose to PS1 giving the LeA antigen
LeB is dependent on the Se and H gene. When all three genes are present, H substance will be made and secreted into tissues. Then the fucosyltransferase can add another fucose to the H substance, making the LeB antigen. Without Se or H, no LeB will be present.
If a person is negative for the A and B antigens, you cannot tell if they are a secretor or not
How do Lewis antigens differ with age?
Newborns type as Le(a-b-) because Lewis antigens are not adsorbed until after birth. The correct phenotype is expressed around age six.
What are some traits of Lewis Antigen expression?
They are always expressed in secretions if Le gene is present.
RBC antigen expression is diminished during pregnancy which is why women can make Anti-LeA
Transfused donor blood will take on the phenotype of the recipient within a few days
What are the disease associations with Lewis system?
Helicobactor pylori uses LeB to bind to gastric epithelial cells to cause gastric ulcers
Le(a-b-) are at risk for Candida and E. coli infections
When would Lewis antibodies be made
Anti-LeA during pregnancy (common)
Anti-LeB can be made by Le(a-b-) or Le(a+b-)
What are some important characteristics of Lewis antibodies?
May bind complement and demonstrate in vitro hemolysis in which case would be clinically significant. Must provide antigen negative blood if hemolysis is seen at AHG phase.
Can rarely form IgG
What is Lewis Substance?
A reagent made to neutralize the activity of anti-LeA or B
made from saliva
if activity is neutralized after incubating with Lewis substance that means Lewis AB are present
Ii Blood Group Summary
Cold reacting antibodies found in 100% of population as an autoantibody (react strongly at 4 degrees)
I and i antigens found on 100% of adults while cord blood is ii until 18 months
I soluble substance found in saliva, serum, breast milk, amniotic fluid, and urine (regardless of Se)
Clinically insignificant but if patient has a strong antibody you can “get rid” of it by using the pre-warm technique
Anti-I associated with Cold hemaglutinin disease
Anti-i associated with infectious mono
What is Autoanti-H
a compound antibody that reacts when both I and H Ags are present
when differentiating between anti-I and anti-IH, test with A1 and O adult cells and A1 and O cord cells
What are the four P blood group antigens?
P1, P, Pk, p
What antigens and antibodies are associated with the P1 and P2 phenotypes
P1 - has P1 and P antigens, will make no Abs
P2 - only makes P antigens so can make anti-P1
Characteristics of the P system
Abs are cold reacting and insignificant
majority of population is P1 positive
Substances found in secretions (hydratid cyst fluid) and bird droppings
Commercial P Substance can be used to neutralize P or P1 antibodies to aid ABID
Autoanti-P is seen in Paroxysmal Cold Hemoglobinurea
