What genes are at play in the ABO blood group system?
What are their gene products?
H gene (chr. 19)
- Produces H substance (a carbohydrate)
ABO gene (chr. 9)
Products act on H substance
- A gene: 1,3-N acetylgalactosaminyl
- B gene: 1,3-galactosyl transferase
- O gene: produces a serum protein product which has no known enzymatic activity
What kind of genotype/phenotype relation does ABO blood-typing have?
When do ABO antibodies arise? What kind of Abs are they?
Anti-A and anti-B Abs are naturally occurring appear spontaneously at 5-6 mo after birth (anti-A, anti-B, antiA,B)
- No need for prior transfusion
- Mostly IgM and some portion is IgG
- Universal blood = type O
- Universal plasma = type AB!
What is the effect of ABO antibodies?
-> intravascular hemolysis
-> severe hemolysis/DIC/death
How is ABO grouping determined?
2 tests are used to determine ABO of transfusion recipient to prevent typing error
- Cell/Forward typing: detection of antigens on RBC by anti-A and anti-B antisera
- Serum/Reverse typing: detection of anti-A and anti-B antibodies by the use of known A and B cells RBC + plasma/reagents -> agglutination
Screening results by blood type:
What is the interpretation of this typing?
FYI? Frequency of ABO blood groups in the US?
O > A > B > AB
ABO blood and plasma compatability?
What is Rh?
- Stands for Rhesus (Rhesus monkey)
- There are 56 Rh antigens known
What are the 5 important Rh antigens?
D locus: D- most immunogenic (commonly referred to as Rh type)
C locus: C and c
E locus: E and e
Rh is synonymous with what?
D (Rh typing means D antigen typing)
So basically, in naming: A pos = A, D positive
What is the Rh type based on the following results?
Frequency of Rh positive and negative phenotypes in the population
- Positive >> negative
- Basically, if you're Asian and Rh-, it's most likely a mistake/artifact
What genotypes reusult in the + and - Rh phenotypes?
Rh positive: DD or Dd
Rh negative: dd
ABO/Rh percentages in Houston?
Do antibodies form to Rh?
- Rh negative individuals do not have anti-Rh; it is NOT naturally occurring/spontaneously developed
- It may be developed post transfusion of Rh positive RBCs or pregnancy or transplant!!
Describe the sensitization of Rh negative individuals to Rh
- 80% of Rh- (healthy) will become sensitized after receiving 1 unit of Rh+ RBCs
- 10% will become sensitized after delivering Rh+ baby if untreated with Rh immunoglobulin
How to handle pregnant Rh- moms?
Rhogram (Rh immunoglobulin)
What can Rh antibodies cause (when an Rh- person with antibodies receive Rh+ blood)?
- Severe hemolytic disease of fetus and newborn (HDFN)
- Hemolytic transfusion reaction (HTR)
T/F: Rh+ platelet transfusion can lead to sensitization. Consequences?
True! (under 2 mL of RBC)
- Rh- cellular blood products (RBC and platelets) to Rh- women of reproductive age whenever possible
T/F: Group A is the most common ABO among all races
False; Type O is the most common
T/F: Type AB plasma can be safely transfused to any individual regardless of ABO type in an emergency
T/F: Rh negative individuals develop anti-Rh spontaneously by age 2 years
T/F: Approximately 15% of Caucasians are Rh negative
True (Asian Americans, almost never)
T/F: If both parents are A+ their children must also be A+
T/F: As risk of Rh sensitization is low, Rh positive RBC can be safely transfuse to Rh negative young women