Immunohematology ABO/Rh (complete)

Question 1

How common are the blood types?

Answer 1

In US white pop’n:
O>A>B>AB

In US black pop’n:
same but more B and less A

Very different throughout the world

O common for South Am, rare in China

B common in Vietnam

OVERALL: AB is the RAREST blood type

Question 2

What are the red cell Ags in the blood types?

Answer 2

O => H Ag

A => A Ag

B => B Ag

AB => split 50/50 A&B

Bombay => h Ag

Question 3

Which ABO antibodies are in the plasma of each blood type?

Answer 3

O => anti-A & anti-B

A => anti-B

B => anti-A

AB => none

Bombay => anti-A, anti-B, & anti-O

Question 4

Persons w/ O blood can receive which type of blood?

Answer 4

O

Question 5

Persons w/ A blood can receive which type of blood?

Answer 5

A & O

Question 6

Persons w/ B blood can receive which type of blood?

Answer 6

B & O

Question 7

Persons w/ AB blood can receive which type of blood?

Answer 7

all types

Question 8

Persons w/ O blood can donate which type of blood?

Answer 8

all types

except Bombay

Question 9

Persons w/ A blood can donate which type of blood?

Answer 9

A & AB

Question 10

Persons w/ B blood can donate which type of blood?

Answer 10

B & AB

Question 11

Persons w/ AB blood can donate which type of blood?

Answer 11

AB

Question 12

What are the possible genotypes of O blood?

Answer 12

OO

Question 13

What are the possible genotypes of A blood?

Answer 13

AA or AO

Question 14

What are the possible genotypes of B blood?

Answer 14

BB or BO

Question 15

What are the possible genotypes of AB blood?

Answer 15

AB

Question 16

What is the antibody class of most ABO isohemagglutinins?

Answer 16

IgM!!!

This is especially important when you think about pregnancy!

Mom doesn’t launch immune response to fetus b/c IgM can’t cross the placenta

Question 17

Explain the ABO Ag situation in a person with Bombay blood type

Answer 17

• Final sugar not placed in “core” Ag b/c they lack the transferase gene that does this
• Therefore no additional sugars (e.g. A or B) can be put on penultimate sugar

Those w/ Bombay blood can still have functioning glycosyltransferases that put A or B on penulti sugar, but they can’t do so w/o final sugar on the end of “core” Ag

Question 18

What are the consequences of a transfusion of non-Bombay blood into a patient with Bombay blood?

Answer 18

Death

Bombay blood has anti-O, anti-A, and anti-B

A non-Bombay transfusion would launch an immuno response on the pt’s own blood

Question 19

Define the crossmatch

Answer 19

A lab test! Done after matching ABO and Rh

• Prospective recipient’s plasma is mixed w/ prospective donor’s RBCs
• If red this indicates hemolysis

NOT compatible if it turns red or there is clumping

Question 20

Explain why the crossmatch is important

Answer 20

• Otherwise complement-mediated hemolysis would occur

- This can lead to acute renal failure

Question 21

Explain how red cells are destroyed following a mismatched transfusion and why this may be devastating to the pt

Answer 21

• Via complement-mediated hemolysis

- Free Hb is then deposited in the kidneys => acute renal failure

Question 22

What are the techniques of a direct antiglobulin test?

Answer 22

• Take recipient RBCs
• Wash them
• Add anti-IgG Ab
• If agglutination, positive test

Question 23

What are the techniques of a indirect antiglobulin test?

Answer 23

• Take donor RBCs
• Add recipient plasma
• Wash unbound proteins
• Add anti-IgG Ab
• Agglutinates if positive

Antiglobulin crosslinks the bound Abs

Question 24

The direct antiglobulin test is designed to answer which questions?

Answer 24

Is there Ab already on these cells?

Question 25

The indirect antiglobulin test is designed to answer which questions?

Answer 25

Is there unexpected Ab to red cell Ags in the plasma of this potential recipient?

Question 26

What is a heterophile Ab?

Answer 26

- Cross-reactive Abs

Question 27

What is a common disease in which one type of heterophile Ab is increased enough to be useful diagnostically?

Answer 27

Infectious mononucleosis! - Abs produced in mono also cross-react w/ horse RBCs - A quick and cheap test!

Question 28

In the Hemolytic Disease of the Newborn explain the consequences of severe hemolysis in the newborn

Answer 28

- Causes high levels of bilirubin (presents as jaundice) | - Bili can cross the BBB and damage the basal ganglia => cerebral palsy or fetal death

Question 29

In the Hemolytic Disease of the Newborn explain the way in which the mother becomes sensitized

Answer 29

- Happens in last trimester, especially at time of delivery - Rh(D)- mom is exposed to Rh(D)+ baby's blood - Mom produces IgM to Rh(D) => becomes IgG and produces memory T cells to Rh(D)+ - Those Abs cannot be used b/c there's no more baby

Question 30

In the Hemolytic Disease of the Newborn explain the class of antibody to Rh(D) the mother makes

Answer 30

IgG CAN cross the placenta in future pregnancies

Question 31

In the Hemolytic Disease of the Newborn explain the consequences of sensitization to subsequent fetuses

Answer 31

- Mom's IgG from previous exposure can now cross the placenta and can attack fetus's RBCs - leads to jaundice and potentially other problems

Question 32

In the Hemolytic Disease of the Newborn explain the role of Rh-immune globulin (RhoGAM)

Answer 32

- Mom receives IgG Ab to Rh(D)+ at the time of delivery - These Abs combine w/fetal RBCs, opsonize them and are destroyed before they immunize her - Whole point is to prevent sensitization (immunization) of mom to Rh(D)+ - Mom must do this at each pregnancy Prevent hemolytic disease of the newborn

Question 33

Explain the situation in which ABO hemolytic disease of the newborn can occur.

Answer 33

- This happens if a mom w/ O blood makes IgG isohemagglutinins - leads to disease if fetus has A, B, or AB blood - no RhoGAM-like Ab for this Remember: - IgG crosses placenta - O blood makes anti-A and anti-B