Hypersensitivity

Question 1

What is the key mediator of Type I hypersensitivity?

Answer 1

IgE antibodies.

Question 2

What is the key mechanism of Type I hypersensitivity?

Answer 2

An allergen cross-links IgE on mast cells and basophils, causing the release of vasoactive mediators.

Question 3

What are some manifestations of Type I hypersensitivity?

Answer 3

Anaphylaxis, hay fever, asthma, hives, and food allergies.

Question 4

What is the key mediator of Type II hypersensitivity?

Answer 4

Antibodies (IgG) that bind to cell surface antigens.

Question 5

What is the key mechanism of Type II hypersensitivity?

Answer 5

Antibody-directed cell destruction via complement activation or ADCC.

Question 6

What are some manifestations of Type II hypersensitivity?

Answer 6

Blood transfusion reactions and erythroblastosis fetalis.

Question 7

What is the key mediator of Type III hypersensitivity?

Answer 7

Soluble antigen-antibody complexes.

Question 8

What is the key mechanism of Type III hypersensitivity?

Answer 8

Immune complexes are deposited in tissues, activating complement and attracting neutrophils.

Question 9

What are some manifestations of Type III hypersensitivity?

Answer 9

Rheumatoid arthritis, lupus, and glomerulonephritis.

Question 10

What is the key mediator of Type IV hypersensitivity?

Answer 10

Cell-mediated immunity, specifically TH1 cells.

Question 11

What is the key mechanism of Type IV hypersensitivity?

Answer 11

Sensitized TH1 cells release cytokines that activate macrophages or cytotoxic T cells, causing cellular damage.

Question 12

What are some manifestations of Type IV hypersensitivity?

Answer 12

Contact dermatitis, tubercular lesions, and graft rejection.

Question 13

What is the role of mast cells and basophils in Type I hypersensitivity?

Answer 13

They release vasoactive mediators after their IgE antibodies are cross-linked by an allergen.

Question 14

What is the role of complement in a Type II reaction?

Answer 14

It is activated by antibodies binding to cell surface antigens, leading to cell destruction.

Question 15

What is the role of complement in a Type III reaction?

Answer 15

It is activated by immune complexes, which attracts neutrophils to the site of deposition, causing inflammation.

Question 16

What is the role of TH1 cells and macrophages in Type IV hypersensitivity?

Answer 16

Sensitized TH1 cells release cytokines that activate macrophages, which then mediate cellular damage.

Question 17

What antigens and antibodies are present in a person with Type A blood?

Answer 17

A antigens on RBCs and anti-B antibodies in the serum.

Question 18

What antigens and antibodies are present in a person with Type B blood?

Answer 18

B antigens on RBCs and anti-A antibodies in the serum.

Question 19

What antigens and antibodies are present in a person with Type AB blood?

Answer 19

Both A and B antigens on RBCs and neither anti-A nor anti-B antibodies in the serum.

Question 20

What antigens and antibodies are present in a person with Type O blood?

Answer 20

Neither A nor B antigens on RBCs but both anti-A and anti-B antibodies in the serum.

Question 21

What is Rh incompatibility?

Answer 21

A condition where an Rh-negative mother is exposed to and produces antibodies against the Rh antigens of an Rh-positive baby.

Question 22

What is erythroblastosis fetalis?

Answer 22

A Type II hypersensitivity reaction in which a mother’s antibodies destroy a subsequent Rh-positive baby’s RBCs.

Question 23

How is Type I hypersensitivity diagnosed?

Answer 23

Via a wheal and flare reaction after an allergen is injected into the skin.

Question 24

How is Type IV hypersensitivity diagnosed?

Answer 24

Via a DTH test, like the Tuberculin Skin Test, where the reaction is assessed after 24-48 hours.

Question 25

How can a complement fixation test be used to detect antigen-antibody complexes?

Answer 25

If complexes are present, they will consume complement, and no lysis of indicator cells will occur.