8/25- Transfusion: ABO-Rh and Compatability

Question 1

What genes are at play in the ABO blood group system?

Chromosomes?

What are their gene products?

Answer 1

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

Question 2

What kind of genotype/phenotype relation does ABO blood-typing have?

Answer 2

Co-dominance

Question 3

When do ABO antibodies arise? What kind of Abs are they?

Answer 3

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!

Question 4

What is the effect of ABO antibodies?

Answer 4

Complement activating

• > intravascular hemolysis
• > severe hemolysis/DIC/death

Question 5

How is ABO grouping determined?

Answer 5

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

Question 6

Screening results by blood type:

Answer 6

Question 7

What is the interpretation of this typing?

Answer 7

Group A

Question 8

FYI? Frequency of ABO blood groups in the US?

Answer 8

O > A > B > AB

Question 9

ABO blood and plasma compatability?

Answer 9

Question 10

What is Rh?

Answer 10

• Stands for Rhesus (Rhesus monkey)
• There are 56 Rh antigens known

Question 11

What are the 5 important Rh antigens?

Answer 11

D locus: D- most immunogenic (commonly referred to as Rh type)

C locus: C and c

E locus: E and e

Question 12

Rh is synonymous with what?

Answer 12

D (Rh typing means D antigen typing)

So basically, in naming: A pos = A, D positive

Question 13

What is the Rh type based on the following results?

Answer 13

Question 14

Frequency of Rh positive and negative phenotypes in the population

Answer 14

• Positive >> negative
• Basically, if you’re Asian and Rh-, it’s most likely a mistake/artifact

Question 15

What genotypes reusult in the + and - Rh phenotypes?

Answer 15

Rh positive: DD or Dd

Rh negative: dd

Question 16

ABO/Rh percentages in Houston?

Answer 16

Question 17

Do antibodies form to Rh?

Answer 17

• 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!!

Question 18

Describe the sensitization of Rh negative individuals to Rh

Answer 18

- 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

Question 19

How to handle pregnant Rh- moms?

Answer 19

Rhogram (Rh immunoglobulin)

Question 20

What can Rh antibodies cause (when an Rh- person with antibodies receive Rh+ blood)?

Answer 20

• Severe hemolytic disease of fetus and newborn (HDFN)
• Hemolytic transfusion reaction (HTR)

Question 21

T/F: Rh+ platelet transfusion can lead to sensitization. Consequences?

Answer 21

True! (under 2 mL of RBC)

• Rh- cellular blood products (RBC and platelets) to Rh- women of reproductive age whenever possible

Question 22

T/F: Group A is the most common ABO among all races

Answer 22

False; Type O is the most common

Question 23

T/F: Type AB plasma can be safely transfused to any individual regardless of ABO type in an emergency

Answer 23

True

Question 24

T/F: Rh negative individuals develop anti-Rh spontaneously by age 2 years

Answer 24

False

Question 25

T/F: Approximately 15% of Caucasians are Rh negative

Answer 25

True (Asian Americans, almost never)

Question 26

T/F: If both parents are A+ their children must also be A+

Answer 26

False

Question 27

T/F: As risk of Rh sensitization is low, Rh positive RBC can be safely transfuse to Rh negative young women

Answer 27

False