Chapter 4: Immunology

Question 1

Helper T cells (CD4)

Answer 1

• Release IL-2 (causes maturation of cytotoxic T cells)
• Release IL-4 (causes B-cell maturation into plasma cells)
• Involved in delayed-type hypersensitivity

Question 2

IL-2: function

Answer 2

Causes maturation of cytotoxic T cells

Question 3

IL-4: function

Answer 3

Causes B-cell maturation into plasma cells

Question 4

Brings in inflammatory cells by chemokine secretion

Answer 4

Delayed-type hypersensitivity

Question 5

Suppressor T cells (CD8)

Answer 5

Regulate CD4 and CD8 cells

Question 6

Cytotoxic T cells (CD8)

Answer 6

Recognize and attack non-self-antigens attached to MHC class 1 receptors (e.g. viral gene productS)

Question 7

Intradermal skin test (i.e., TB skin test): type of immunity

Answer 7

cell-mediated immunity

Question 8

Infections associated with defects in cell-mediated immunity

Answer 8

Intracellular pathogens (TB, viruses)

Question 9

MHC class 1 (A, B, C)

Answer 9

CD8 cell activation

• Present on all nucleated cells
• Single chain with 5 domains
• Target for cytotoxic T cells (binds T cell receptor)

Question 10

MHC class II (DR, DP, and DQ)

Answer 10

CD4 cell activation

• Present on antigen-presenting cells (e.g., monocytes, dendrites)
• 2 chains with 4 domains each
• Activates helper T cells (binds T cell receptor)
• Stimulates antibody formation after interaction with B cell surface IgM

Question 11

Mechanism of immune response to viral infection

Answer 11

Endogenous viral proteins are produced, are bound to class I MHC, go to cell surface, and are recognized by CD8 cytotoxic T cells

Question 12

Mechanism of immune response to bacterial infection

Answer 12

Endocytosis, proteins get bound to Class II MHC molecules, go to cell surface, recognized by CD4 helper T cells -> B cells which have already bound to the antigen are then activated by the CD4 helper T cells; they then produce the antibody to that antigen and are transformed to plasma cells and memory B cells.

Question 13

Natural Killer Cells

Answer 13

• Not restricted by MHC, do not require previous exposure, do not require antigen presentation
• Not considered T or B cells
• Recognize cells that lack self-MHC
• Part of the body’s natural immunosurveillance for cancer

Question 14

Initial antibody made after exposure to antigen. It is the largest antibody, having 5 domains (10 binding sites)

Answer 14

IgM

Question 15

Most abundant antibody in body.
Responsible for secondary immune response.
Can cross the placenta and provide protection in newborn period.

Answer 15

IgG.

Question 16

Two signals that cause activation of T and B cells

Answer 16

1. Alloantigen binds to antigen specific receptors. (TCR - T cells; IgM - B cells)
2. IL-1 release by APC.
   CD4 helper T cells release IL-2/4 which provide help for CD8 T cells and B-cell activation.

Question 17

Endogenous antigen processing and presentation

Answer 17

Endogenous proteins are degraded into peptides that are transported to ER. Peptides bind to MHC-1 and transported to surface of APC. CD8 cells recognize complex by way of TCR complex.

Question 18

Exogenous antigen processing and presentation

Answer 18

Exogenous antigen is broken down into peptide fragments in endosomes. Class-2 molecules transport to endosome, bind the peptide, and delivered to surface of APC cell, where they are recognized by CD4+ cells.

Question 19

Found in secretions, in Peyer’s patches in gut, and in breast milk (additional source of immunity in newborn); helps prevent microbial adherence and invasion in gut.

Answer 19

IgA

Question 20

Membrane-bound receptor on B cells (serves as an antigen receptor)

Answer 20

IgD

Question 21

Allergic reactions, parasite infections

Answer 21

IgE

Question 22

Opsonins

Answer 22

IgM, IgG

Question 23

Fix complement

Answer 23

IgM, IgG (requires 2 IgGs, or 1 IgM)

Question 24

Have multiple binding sites to the antigen at multiple epitopes

Answer 24

Polyclonal antibodies

Question 25

Have only 1 binding site to 1 epitope

Answer 25

Monoclonal antibodies

Question 26

Immediate hypersensitivity reaction (allergic reaction) eosinophils have IgE receptors for the antigen and release major basic protein, which in turn activates mast cells and basophils, which release histamine, serotonin and bradykinin

Answer 26

Type 1 | Ex: bee stings, peanuts, hay fever

Question 27

Hypersensitivity: IgG or IgM reacts with cell-bound antigen

Answer 27

Type 2: | Ex: ABO blood incompatibility, Graves' disease, myasthenia gravis

Question 28

Hypersensitivity: Immune complex deposition

Answer 28

Type 3 | Ex: Serum sickness, SLE

Question 29

Hypersensitivity: Delayed-type hypersensitivity - antigen stimulation of previously sensitized T cells

Answer 29

Type 4 | Ex: TB sin test (PPD), contact dermatitis

Question 30

Major source of histamine in the blood

Answer 30

Basophils

Question 31

Major source of histamine in tissue

Answer 31

Mast cells

Question 32

Primary lymphoid organs

Answer 32

Liver, bone, thymus

Question 33

Secondary lymphoid organs

Answer 33

Spleen and lymph nodes

Question 34

Immunologic chimera

Answer 34

2 different cell lines in one individual (e.g., bone marrow transplant patients)

Question 35

IL-2 function in malignancy

Answer 35

- Converts lymphocytes to lymphokine-activated killer (LAK) cells by enhancing their immune response to tumor. - Also converts lymphocytes into tumor-infiltrating lymphocytes (TILs) - Has shown some success for melanoma

Question 36

When do you give tetanus toxoid to tetanus-prone wounds?

Answer 36

Always give tetanus toxoid unless the patient has had > 3 doses

Question 37

Criteria for tetanus-prone wounds

Answer 37

``` > 6 hours old. Obvious contamination and devitalized tissue. Crush. Burn. Frostbite. Missile injuries. ```

Question 38

When would you give tetanus immune globulin with tetanus prone wounds?

Answer 38

Give only with tetanus-prone wounds in patients who have not been immunized or if immunization status is unknown.