The human blood group systems. Blood transfusion procedures. The anaphylactic reaction.

Question 1

Blood group definition

Answer 1

A classification based on the presence or absence of hereditary antigens on the surface of red blood cells

Question 2

ABO blood grouping system

Answer 2

Antigens expressed on the surface of Red Blood Cells are several different sugars synthesized by a series of GLYCOSYL TRANSFERASE

Question 3

H-antigen

Answer 3

All individuals express
FUCOSYL TRANSFERASE
- Result in an antigen containing terminal fucose molecules on the RBC surface
- If this is the only antigen present = blood type O

Question 4

A-antigen

Answer 4

If an individual expresses additional
N-ACETYLGALACTOSAMINE TRANSFERASE
-the H-antigen will have N-acetylgalactosamine bound to it, producing the A antigen
-Presence of the A-antigen results in blood type A

Question 5

B-antigen

Answer 5

GALCTOSYL TRANSFERASE

• H-antigen will have galactose bound to it, producing B antigen
• Presence of the B-antigen results in blood type B

Question 6

Blood type AB

Answer 6

Results from the expression of both additional enzyme activities and the resulting the presence of both A and B antigens on RBCs

Question 7

Blood type A

Answer 7

Has A antigen present on RBC and Anti - B antibodies present in the serum.
Genotype is either AA or AO

Question 8

Blood type B

Answer 8

Has B antigen present on RBC and Anti - A antibodies present in the serum.
Genotype is either BB or BO

Question 9

Blood type AB

Answer 9

A antigen and B antigen present on RBC

Antibodies present in serum: none

Question 10

Blood type O

Answer 10

Antigen present in red blood cells: none
Antibodies present in serum: anti - A and anti - B
Genotype is OO

Question 11

The antibodies produced against A and B antigens

Answer 11

Are Ig-M antibodies. Do not pass the placenta

Question 12

Rh blood grouping System

Answer 12

D antigen is the strongest antigen

A dominant allele

Question 13

Rh positive

Answer 13

Genotype: DD or Dd

Antigen produced: D, ant IgG type antibody

Question 14

Why is this relevant regarding pregnancy?

Answer 14

Because anti-D production requires a first exposure
Rh- mothers that are pregnant with a second Rh+ child after potential gestational exposure to the Rh+ blood of their first-born are likely to produce anti-D which can cross the placenta and bind fetal RBCs, inducing an immune response and RBC lysis, harming the fetus.

Question 15

Blood Transfusion Procedures

Answer 15

You should do a TWO-SIDED TEST of both the donor blood and recipient blood for antibodies against each other’s blood.
You should also mix the two blood types in a sample tube and see if they AGGLUTINATE before attempting transfusion.
Before transfusion, the blood should also be prewarmed to body temperature to prevent a nonspecific response to cold antigens.
If you screwed up and gave the wrong blood in a transfusion and there is an immunological response,
ANTIHISTAMINES should be given immediately (read about anaphylaxis for why).
If the response is severe and life-threatening, corticosteroids should also be given, along with other life-saving drugs like epinephrine.

Question 16

The Anaphylactic Reaction

Answer 16

Release of the chemical mediators stored in mast cells
promotes the allergic reactions known as
immediate hypersensitivity reactions,
because they occur within a few minutes after penetration by an antigen.
There are many examples of immediate hypersensitivity reaction;
a dramatic one is anaphylactic shock, a potentially fatal condition.
The process of anaphylaxis consists of the following sequential events:
The first exposure to an antigen
(allergen), such as bee venom, results in production of the IgE class of immunoglobulins (antibodies) by plasma cells. This IgE then binds to the membranes of mast cells*.
A second exposure to the antigen results in binding of the antigen to IgE on the mast cells.
Histamine causes
*contraction of smooth muscle (mainly of the bronchioles)
*dilates and increases blood vessel permeability
(mainly in postcapillary venules). Lowering the blood pressure