L.4 Antigen/Antibody Reaction

Question 1

What are allogenic antigens?

Answer 1

Nonself antigens.

Question 2

What are autologous antigens?

Answer 2

Self-antigens.

Question 3

Define haptens.

Answer 3

Partial antigens that require a carrier molecule to elicit an immune response.

Question 4

What are antigenic determinants also known as?

Answer 4

Epitopes.

Question 5

What are antibodies made of?

Answer 5

Glycoproteins made of 4 polypeptide chains joined by disulfide bonds.

Question 6

How many heavy and light chains do antibodies include?

Answer 6

2 heavy chains and 2 light chains (2 kappa or 2 lambda chains).

Question 7

What determines the antibody class?

Answer 7

The constant region consisting of heavy chains (Fc region).

Question 8

List the classes of antibodies.

Answer 8

• IgG
• IgA
• IgM
• IgD
• IgE

Question 9

What is the function of the variable region of antibodies?

Answer 9

Binds the antigen.

Question 10

Where are antibodies found in the body?

Answer 10

Tears, saliva, breast milk, plasma/serum.

Question 11

What are antibodies also known as?

Answer 11

Immunoglobulins.

Question 12

Which antibodies are the most important in transfusion?

Answer 12

IgM and IgG.

Question 13

What type of cells process antigens?

Answer 13

APCs specifically B cells.

Question 14

What do B cells present antigens to?

Answer 14

T cells via TCR-MHC complex.

Question 15

What do T cells produce to activate B cells?

Answer 15

Cytokines.

Question 16

What do activated B cells convert to?

Answer 16

Plasma cells or memory B cells.

Question 17

What do plasma cells secrete?

Answer 17

Immunoglobulins with a specificity for the stimulating antigen.

Question 18

Where do memory B cells reside?

Answer 18

In lymphoid organs.

Question 19

What happens to memory B cells after re-exposure to an antigen?

Answer 19

They can rapidly produce antibodies.

Question 20

What is intravascular haemolysis?

Answer 20

Direct lysis of RBCs in the circulation, resulting in release of haemoglobin into plasma.

Free haemoglobin can lead to uncontrolled clotting, hypotension, and organ failure due to poor perfusion.

Question 21

What commonly causes intravascular haemolysis?

Answer 21

Most often caused by IgM antibodies that are capable of activating the complement system.

These antibodies lead to the lysis of red blood cells in the circulation.

Question 22

What occurs during extravascular haemolysis?

Answer 22

RBCs are coated with antibodies and removed from circulation by macrophages in the spleen or liver.

Haemoglobin is not released into circulation, making this process typically less dramatic than intravascular haemolysis.

Question 23

What characterizes the primary antibody response?

Answer 23

Initial responses tend to be slow, with low titre IgM antibodies.

This response occurs upon the first exposure to an antigen.

Question 24

What happens during the secondary antibody response?

Answer 24

Rapid rise in titre with the destructive capabilities of IgG class antibodies.

This occurs upon subsequent exposures to the same antigen.

Question 25

What are the two steps involved in antigen-antibody reactions detected by agglutination?

Answer 25

* Sensitization * Lattice formation ## Footnote Sensitization involves antibody binding to antigen without visible agglutination; lattice formation involves cross-linking of antibody-coated cells.

Question 26

What is zeta-potential in relation to RBCs?

Answer 26

Zeta-potential keeps RBCs apart, making them less likely to be agglutinated by IgG antibodies. ## Footnote IgM antibodies are more likely to cause direct agglutination.

Question 27

What are monoclonal antibodies?

Answer 27

Antibodies produced by a single clone of B cells with one specificity. ## Footnote They are used in various therapeutic and diagnostic applications.

Question 28

What are polyclonal antibodies?

Answer 28

Antibodies produced by multiple clones of B cells with different specificities. ## Footnote They are often used in research and diagnostics due to their ability to recognize multiple epitopes.

Question 29

What is the first step in monoclonal antibody production?

Answer 29

Mice are immunized with antigen.

Question 30

What is harvested from mice after immunization in monoclonal antibody production?

Answer 30

The spleens are harvested for immune cells.

Question 31

What process involves fusing antibody-forming cells with tumor cells in monoclonal antibody production?

Answer 31

Fusion.

Question 32

What are the cells formed by the fusion of antibody-forming cells and tumor cells called?

Answer 32

Hybridomas.

Question 33

What is done to hybridomas in monoclonal antibody production?

Answer 33

The hybridomas are screened for the production of desired antibody.

Question 34

Each hybridoma is descended from what type of cell?

Answer 34

A single B-cell clone.

Question 35

What does the hybridoma cell line produce?

Answer 35

The same antibody molecule.

Question 36

What are autoantibodies?

Answer 36

Antibody made against your own antigens.

Question 37

In which diseases are autoantibodies commonly seen?

Answer 37

Autoimmune diseases e.g. SLE.

Question 38

What causes the formation of autoantibodies?

Answer 38

A break in immune tolerance.

Question 39

What are alloantibodies?

Answer 39

Antibodies made against foreign antigens from another person.

Question 40

When do alloantibodies typically occur?

Answer 40

In cases of blood transfusions, pregnancy, or organ transplants.

Question 41

What test detects alloantibodies?

Answer 41

Antibody screen test.

Question 42

What is the function of the complement system?

Answer 42

Helps destroy RBCs either within blood vessels or by making RBCs easier for macrophages to destroy.

Question 43

What is intravascular hemolysis?

Answer 43

Destruction of RBCs inside blood vessels.

Question 44

What is extravascular hemolysis?

Answer 44

Destruction of RBCs by macrophages outside blood vessels.

Question 45

What type of antibody primarily binds to antigens on RBC surfaces in the complement system?

Answer 45

IgM.

Question 46

What triggers the classical pathway of the complement system?

Answer 46

Antibodies binding to antigens.

Question 47

What is the role of C3 in the complement cascade?

Answer 47

C3 splits into C3a and C3b; C3b binds to RBC surface and marks it for destruction.

Question 48

What forms the membrane attack complex (MAC)?

Answer 48

A later stage in the complement cascade.

Question 49

What happens to RBCs if MAC forms?

Answer 49

The RBC is ruptured inside the blood vessel.

Question 50

What is necessary for macrophages to recognize RBCs during extravascular hemolysis?

Answer 50

C3b deposition.

Question 51

What activates the alternative pathway of the complement system?

Answer 51

Foreign cell surface constituents e.g. bacteria.