Immunohematology (Blood Bank Testing)

Question 1

H Antigen

Answer 1

considered the foundation onto which both A & B antigens are created

Question 2

Bombay Phenotype

Answer 2

Rare phenotype without even the H antigen

Question 3

How do antigens attach to the RBC surface?

Answer 3

ABO blood group antigens are attached to oligosaccharide chains that project above the RBC surface. These chains are attached to lipids that lie in the RBC membrane

Question 4

3 Features of Antibodies’ Clinical Significance

Answer 4

Antibodies destroy RBCs in vivo, cause HDN, and are common.

Question 5

Types of Autoimmune Hemolytic Anemias

Answer 5

Warm-reactive autoantibodies. Cold-reactive autoantibodies: cold hemagglutinin dz, Paroxysmal cold hemoglobinuria

Question 6

Types of Alloimmune Hemolytic Anemias

Answer 6

Hemolytic dz of the newborn (HDN), Hemolytic transfusion reactions.

Question 7

Third type of Immune Hemolytic Anemia

Answer 7

Drug Induced

Question 8

Autograft

Answer 8

Tissue from a person’s own body being replaced. (Blood removed and returned, a vein from the leg being used in the neck.

Question 9

Allograft

Answer 9

A same-species transplant. Most organ transplants or blood transplants.

Question 10

Xenograft

Answer 10

Inter-species transplant

Question 11

What is unique about AB antibodies?

Answer 11

They are the ONLY system wherein the reciprocal antibodies are consistently and predictably present in the sera of people who have had no exposure to human red cells! (Usually exposure is required to make antibodies.

Question 12

Most important Blood Group system for transfusion practice?

Answer 12

ABO. Also the first to be identified.

Question 13

Isohemaglutinins

Answer 13

Naturally occurring antibodies & complete antibodies (IgM class) against A & B antigens.

Question 14

ABO antibodies

Answer 14

IgM large enough to produce visible agglutination. Formed w/out prior sensitization to the foreign RBC. Thought to have formed from encountering similar antigenic determinants on micro-organisms.

Question 15

ABO Blood types & their corresponding antibodies

Answer 15

Type A -> B antibody. Type B -> A antibody. Type AB -> no antibody. Type O -> A & B antibodies.

Question 16

What are the three tests that must be performed every time there is a transfusion?

Answer 16

Forward Grouping, Reverse Grouping, Crossmatching.

Question 17

Forward Grouping

Answer 17

Reaction of patient’s red blood cells (unknown) with Reagent anti-A & anti-B antisera (known)

Question 18

Reverse Grouping

Answer 18

Reaction of patient serum (unknown) with reagent Group A & Group B cells (known)

Question 19

Crossmatching

Answer 19

Last step before transfusion. Mix donor RBC w/recipient’s plasma & test for rxn.

Question 20

HDN: Hemolytic Dz of the Newborn

Answer 20

AKA Erythroblastosis fetalis. Occurs secondary to trans-placental transfer of maternal antibodies. Most commonly, RH incompatibility (“could” be ABO). Rh HDN occurs with an Rh (-) mother, Rh (+) father, firstborn OK, in subsequent babies affected after the mother’s been sensitized. Anti D antibodies are IgG, and are able to pass across the placenta.

Question 21

Tx for HDN

Answer 21

Mother immunized with RhoGam (Rh immune globulin).

Question 22

Rh factors: Fisher-Race Theory

Answer 22

Allelic genes: Dd, Cd, and Ee. Antigens: Cc, D, Ee. **NO “d” ANTIGEN! Rh (+) persons are D antigen (+), Rh negative persons are D (-), no “d” has been discovered. D is the most antigenic of this group, Anti-D IgG is a STRONG antibody!

Question 23

Only 2 ways for an Rh- person to express Rh antibodies

Answer 23

Placental sensitization, transfusion.

Question 24

D’u’

Answer 24

2-3% of people initially appearing Rh (-) are actually D’u’ (+). In serum testing Anti-D reagents coat the weak D cells but no visible agglutination occurs. Screening for Weak D involves adding Anti-Human Globulin, an indirect antiglobulin test.