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Block Two > HRR: hypersensitivity > Flashcards

HRR: hypersensitivity Flashcards

1
Q

Define hypersensitivity reaction

A

Hypersensitivity occurs when the immune response is triggered and maintained inappropriately.

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2
Q

What are some immune reactions associated with hypersensitivity

A

-Immune response is inadequately controlled

-Immune response is directed against normally harmless antigens

-Immune response inappropriately targets host tissues

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3
Q

What are the 4 types of hypersensitivity reactions?

A

-Immediate hypersensitivity (type I)

-Antibody-mediated hypersensitivity (type II)

-Immune complex-mediated hypersensitivity (type III)

-Cell mediated hypersensitivity (type IV)

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4
Q

Describe immediate hypersensitivity

A

Also known as an allergic reaction or allergy, these occur rapidly, and clinical manifestations may be seen locally or systemically

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5
Q

What interaction triggers immediate hypersensitivity

A

Antigen interacts with IgE on mast cells

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6
Q

Describe the mechanism of developing an immediate hypersensitivity reaction

A

-An allergen enters the mucosal lining and is taken up by a dendritic cell or B cell

-Antigen presentation occurs. A dendritic cell will present to a naïve T cell, and a B cell will present to a Th2 helper cell. If it is a dendritic cell, the T cell matures to Th2 and interacts with a B cell

-B cell becomes a plasma cell that produces IgE

-IgE binds to FceRI on mast cells

-Repeat exposure occurs between IgE on mast cells and the antigen

-The mast cell is activated and releases various vasoactive amines (immediate reaction) and cytokines (late-phase reaction) that lead to reaction.

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7
Q

Explain how allergen binding to IgE on mast cells results in release of various chemicals

A

Binding of an allergen with cross-linking of IgE results in phosphorylation of ITAMs. This then initiates several signaling pathways that lead to the release of mast cell granules.

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8
Q

what is the histiopathology of type I hypersensitivity reactions

A

vascular dilation, edema, smooth muscle contraction, mucus production, tissue injury, inflammation

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9
Q

What do vasoactive amines lead to?

A

Vascular dilation and smooth muscle contraction

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10
Q

What do proteases lead to?

A

Tissue damage

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11
Q

What do prostaglandins lead to?

A

Vascular dilation

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12
Q

What do leukotrienes lead to?

A

Smooth muscle contraction

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13
Q

What to cytokines lead to?

A

Inflammation/ leukocyte recruitment; part of the late response

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14
Q

What factors cause smooth muscle spasm

A

Leukotrienes C4 and D4, histamine, prostaglandin D2, and PAF

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15
Q

Describe chronic allergic disease

A

-Upon epithelial barrier injury, epithelial cells secrete IL-25, IL-33, and TSLP

-These drive T cells to differentiate into Th2 and Tfh helper cells

-The Th cells produce IL-5 and IL-13 upon repeat exposure to antigen

-These stimulate eosinophils and chronic allergic inflammation

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16
Q

Name the prototypes and basic pathology associated with immediate hypersensitivity reaction

A

-Hay fever: inflamed airways and mucous secretion

-Food allergies: contraction of intestinal muscle

-Asthma: bronchial smooth muscle hyperactivity causes airway obstruction

-Anaphylaxis: vascular dilation leads to shock; edema leads to airway obstruction

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17
Q

Describe the general mechanism of antibody-mediated hypersensitivity

A

IgG and IgM antibodies bind to antigens on target cells or tissues and lead to phagocytosis/lysis via activated complement or Fc receptors

18
Q

What are the three major mechanisms involved in antibody mediated disease

A

-Opsonization and phagocytosis

-Activating complement

-Interfering with normal cellular function

19
Q

what is the histopathology of type II hypersensitivity reactions

A

phagocytosis and lysis of cells, inflammation, and sometimes functional derangements without cell or tissue injury

20
Q

Describe immune complex hypersensitivity

A

Antigen-antibody complexes formed in circulation deposit in blood vessels, leading to complement activation and acute inflammation. These tend to be systemic.

21
Q

Which tissues/organs are typically impacted by immune complex hypersensitivity

A

Kidney, joints, small blood vessels

22
Q

Describe the general mechanism of immune complex hypersensitivity

A

-Complexes form in a blood vessel

-Complexes deposit into the wall of the vessel. Here, they fix complement and activate neutrophils

-Inflammation and tissue injury occur. Platelets aggregate and vasculitis happens.

23
Q

What are the two types of cell reactions in T cell mediated hypersensitivity

A

-Cytokine mediated inflammation in which cytokines are produced by CD4+ T cells

-Direct cell cytotoxicity mediated by CD8+ T cells

24
Q

CD4+ T cell mediated hypersensitivity reactions: general characteristics and main example

A

They’re chronic and destructive; the big example is delayed-type hypersensitivity. This is when antigens are introduced into the skin of a previously immunized individual, and there is a detectable reaction in 24-48 hours. Biggest example is a TB test.

25
Q

Autoimmune hemolytic anemia: type of reaction, mechanism, pathology

A

-Type II
-Opsonization and phagocytosis
-Hemolysis and anemia

26
Q

autoimmune thrombocytopenic purpura

A

-Type II
-Opsonization and phagocytosis
-Bleeding

27
Q

Goodpasture syndrome: type of reaction, mechanism, pathology

A

-Type II
-Complement and Fc receptor mediated inflammation
-Nephritis and lung hemorrhage

28
Q

Graves’ disease: type of reaction, mechanism, pathology

A

-Type II
-Antibody-mediated TSH receptor stimulus
-Hyperthyroidism

29
Q

Myasthenia gravis: type of reaction, mechanism, pathology

A

-Type II
-Antibody inhibits Ach binding
-Muscle weakness and paralysis

30
Q

Pemphigus vulgaris: type of reaction, mechanism, pathology

A

-Type II
-Antibody-mediated disruption of intracellular adhesion
-Skin vesicles

31
Q

Pernicious anemia: type of reaction, mechanism, pathology

A

-Type II
-Neutralization of intrinsic factor and decreased absorption of B12
-Anemia due to abnormal erythropoiesis and nerve damage

32
Q

Rheumatic fever: type of reaction, mechanism, pathology

A

-Type II
-Inflammation and macrophage activation
-Myocarditis and arthritis

33
Q

Lupus erythematous: type of reaction, pathology

A

-Type III
-Nephritis, arthritis, vasculitis

34
Q

Polyarteritis nodosa: type of reaction, pathology

A

-Type III
-Vasculitis

35
Q

Post-streptococcal glomerulonephritis: type of reaction, pathology

A

-Type III
-Nephritis

36
Q

Serum sickness: type of reaction, pathology, cause

A

-Type III
-Systemic vasculitis
-Receiving antibodies from other individuals or species

37
Q

Describe the arthus reaction

A

Type III reaction; repeated injections of a protein into the same site leads to a hemorrhagic and necrotic reaction. A localized immune complex mediated vasculitis

38
Q

Granulomatous inflammation is seen in what kind of hypersensitivity?

A

CD4+ T cell mediated hypersensitivity; specifically, prolonged DTH reaction

39
Q

Contact dermatitis is an example of what kind of hypersensitivity

A

Delayed hypersensitivity aka T cell mediated hypersensitivity

40
Q

Describe CD8+ T cell mediated cytotoxicity

A

CD8+ CTLs kill antigen-expressing target cells directly

41
Q

What are two examples of CD8+ T cell mediated hypersensitivity

A

Type I diabetes and graft rejections

Block Two (30 decks)

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