Inflammation-Hypersensitivity Reactions

Question 1

What mediates Type I Hypersensitivity reactions?

Answer 1

IgE antibodies

Question 2

What is Type I also known as?

Answer 2

Immediate anaphylaxis

Question 3

What are the types of anaphylaxis?

Answer 3

General: bronchoconstriction, contraction of smooth muscle, increases in vascular permeability, often fatal, rare

Local: operates via binding of allergen to IgE antibodies on surface of mast cells or basophils; release of histamine causes clinical signs of acute inflammtion

Question 4

What mediates Type II Hypersensitivity reactions?

Answer 4

IgG or IgM antibodies reacting with cell surface antigens or haptens

Question 5

What are the 4 main modes of cell destruction in Type II hypersensitivity?

Answer 5

1. phagocytosis of antibody-coated cells by liver, splenic, or tissue macrophages
2. complement-mediated lysis of antibody-coated cells
3. antibody-dependent cell-mediated cytotoxicity by killer cells
4. surface receptor endocytosis or down regulation

Question 6

What phases do all hypersensitivity reactions have?

Answer 6

Sensitation phase: previous exposure, develop specific immune response

Effector phase: pathology

Question 7

what are the ways in which Type II hypersensitivities can be taken care of (good or bad)?

Answer 7

• -Opsonization via IgG antibodies
• -Opsonization or lysis via complements (kick off the MAC or C3b can causes phagocytosis)
• -Antibody-dependent cell-mediated cytotoxicity (ADCC) (IgG, killer cells have FcR that bind tissue cell)
• -Receptor blockade/removal (antibody doesnt allow hormone to bind or antibody/receptor complex gets internalized)
• -Antibody-mediated cellular dysfunction (antibody causes cell to perform or not perform, regardless of stim by hormones)

Question 8

What is the overall pathway of the Type III Hypersensitivity reaction?

Answer 8

Ag-Ab complex>deposition>neutrophil and macrophage activation by FcR>complement cascade

Question 9

What is the basis of Type III hypersensitivity?

Answer 9

combination of soluble antigen with circulating IgG or IgM antibodies to form “immune complexes”

Question 10

What is an Arthus reaction?

Answer 10

immune complexes are formed locally in blood vessels and tissues

Question 11

What is the characteristic lesion of Type III hypersensitivity?

Answer 11

vasculitis

Question 12

What is Type IV hypersensitivity also known as?

Answer 12

Cell-mediated Delayed Type Hypersensitivity (DTH)

Question 13

What mediates Type IV hypersensitivity?

Answer 13

T cells and macrophages

Question 14

Does the individual have to be sensitized for a Type IV reaction?

Answer 14

Yes

Question 15

What is DTH an extension of?

Answer 15

Normal T cell mediated immune responses

Question 16

What are some examples of Type IV hypersensitivity?

Answer 16

Jones Mote (cutaneous basophil hypersensitivity)
Tuberculin reaction
contact sensitivity

Question 17

What is a Type IV hypersensitivity reaction due to?

Answer 17

activation of specific T cells which release lymphokines to attracte macrophages and more lymphocytes

Question 18

What may happen to a lesion in chronic DTH?

Answer 18

development of epitheloid cells or giant cells (macrophages for both)

These cells along with T cells kill infected cells, causing caseous necrosis at center of reaction

Question 19

What happens to the lesion if the organism is killed? If not?

Answer 19

Killed: lesion is repaired by fibrosis
Not: caseous necrosis is walled off by CT, forming granuloma; lesion can become calcified or liquefied