Hypersensitivity and Autoimmunity

Question 1

What is the difference between immunity and hypersensitivity?

Answer 1

Immunity eliminates foreign antigens; hypersensitivity is an abnormal reaction to them.

Question 2

How many types of hypersensitivity reactions are there?

Answer 2

Four (Types I–IV).

Question 3

Which hypersensitivity types are antibody-mediated?

Answer 3

Types I, II, and III.

Question 4

Which hypersensitivity type is T cell–mediated?

Answer 4

Type IV.

Question 5

What antibody is involved in Type I hypersensitivity?

Answer 5

IgE.

Question 6

What are common triggers of Type I hypersensitivity?

Answer 6

Environmental antigens (e.g., pollen, food, insect venom).

Question 7

What is the role of mast cells in Type I reactions?

Answer 7

They release chemical mediators like histamine when IgE binds to antigen.

Question 8

What is an atopic individual?

Answer 8

Someone genetically predisposed to developing allergies.

Question 9

What is an allergen?

Answer 9

A sensitizing antigen that triggers an allergic response.

Question 10

What is anaphylaxis?

Answer 10

A severe, life-threatening systemic IgE-mediated hypersensitivity reaction.

Question 11

What causes the symptoms of anaphylaxis?

Answer 11

Release of mediators causing vasodilation and bronchoconstriction.

Question 12

What is the treatment for anaphylaxis?

Answer 12

Epinephrine.

Question 13

What is the goal of desensitization therapy?

Answer 13

To produce IgG antibodies that bind allergen before IgE can.

Question 14

What happens in Type II hypersensitivity?

Answer 14

Antibodies bind to cell/tissue antigens, activating complement and causing cell lysis.

Question 15

Give an example of a Type II hypersensitivity reaction.

Answer 15

Blood transfusion reaction.

Question 16

What happens in Type III hypersensitivity?

Answer 16

Antibody-antigen complexes form, activate complement, and cause inflammation and tissue damage.

Question 17

Give an example of Type III hypersensitivity.

Answer 17

Systemic lupus erythematosus (SLE).

Question 18

What is Type IV hypersensitivity also known as?

Answer 18

Delayed-type hypersensitivity.

Question 19

How long does Type IV hypersensitivity take to occur?

Answer 19

24–48 hours.

Question 20

What cells mediate Type IV hypersensitivity?

Answer 20

T cells.

Question 21

What are examples of Type IV hypersensitivity?

Answer 21

TB skin test, poison ivy, some fungal/parasitic infections.

Question 22

How does the TB skin test work?

Answer 22

It elicits a delayed inflammatory reaction in previously infected individuals.

Question 23

What is autoimmunity?

Answer 23

An immune response against one’s own cells and tissues.

Question 24

Why doesn’t the immune system normally attack self?

Answer 24

It develops tolerance to self-antigens.

Question 25

What are three mechanisms that may cause autoimmunity?

Answer 25

Altered self-antigens, cross-reacting antibodies, or defective regulatory T cells.

Question 26

What factors increase risk of autoimmune disease?

Answer 26

Genetics, gender (female), and infections (especially viral).

Question 27

What is systemic lupus erythematosus (SLE)?

Answer 27

A chronic autoimmune disease affecting connective tissue throughout the body.

Question 28

What causes tissue damage in lupus?

Answer 28

Immune complexes deposit in tissues and activate complement, triggering inflammation.

Question 29

What is a hallmark physical sign of lupus?

Answer 29

Butterfly-shaped skin rash across the cheeks and nose.

Question 30

Why is immune suppression sometimes necessary?

Answer 30

To prevent autoimmunity, transplant rejection, and Rh hemolytic disease in newborns.

Question 31

What are some immune suppression methods?

Answer 31

Radiation, immunosuppressive drugs, corticosteroids, and gamma globulin.

Question 32

How does gamma globulin help prevent Rh hemolytic disease?

Answer 32

It contains antibodies that prevent maternal immune activation against fetal Rh antigens.