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Immunology Final > Hypersensitivities and Immunopathologies > Flashcards

Hypersensitivities and Immunopathologies Flashcards

1
Q

What do hypersensitivity reactions target?

A

Self antigens or foreign antigens

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2
Q

What are Type I Hypersensitivities?

A

Allergic or immediate hypersensitivity reactions

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3
Q

When do Type I hypersensitivities occur?

A

Within minutes or hours after antigen exposure

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4
Q

What percent of the population suffers from Type I hypersensitivities?

A

54%

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5
Q

Explain the initial exposure when an allergen enters the body.

A

1) APC eats it
2) APC presents peptides from allergen on MHC II
3) Helper T cells are activated and differentiate into Th2 bias
4) Th2 cells activate B cells that are specific to that allergen
5) B cells make IgE

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6
Q

What cytokines cause the class- switching to IgE in Type I hypersensitivities?

A

IL-4 and IL-13

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7
Q

How long do IgE antibodies live for?

A

In blood only about a day.

If they are attached to mast cells that have a half life of several weeks

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8
Q

Will all people have an initial allergic reaction to the first exposure of an allergen?

A

No, it takes a while for the IgE antibodies to accumulate and load onto the mast cells

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9
Q

How many exposures does it take to activate mast cells?

A

the second exposure

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10
Q

When does an allergic reaction occur?

A

when the chemistry is released from the mast cell

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11
Q

What chemistry is released from an early phase reaction (immediate)?

A

Vasoactive amines (histamine), proteases, prostaglandins

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12
Q

What chemistry is released from a late phase reaction (6-24 hours)?

A

IL-4 and TNF pull in other WBCs (neutrophils and eosinophils

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13
Q

What cells are released during an allergic reaction? Name them in order in which they are released.

A

1) Mast cells
2) Basophils
3) Eosinophils

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14
Q

Where are mast cells located?

A

Tissues

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15
Q

When are mast cells released during an allergic reaction?

A

Immediate response

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16
Q

Where are basophils located?

A

They are brought into the tissue from the blood by signals sent by mast cells

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17
Q

When are basophils released during an allergic reaction?

A

Rapid response

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18
Q

Where are eosinophils located?

A

Recruited from bone marrow (T helper secreting IL-5)

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19
Q

When are eosinophils released during an allergic reaction?

A

Their response is delayed… they are a prominent player in chronic allergic reactions

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20
Q

What 2 types of cells associated with allergic reaction have receptors for IgE?

A

Mast cells and basophils

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21
Q

What type of antibodies do non-atopic individuals produce?

A

IgG

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22
Q

What type of antibodies do atopic individual produce?

A

large quantities of IgE antibodies

23
Q

What is the hygiene hypothesis?

A

The theory that the rise in chronic inflammatory diseases, especially allergies and asthma, is an unintended consequence of a reduction in exposure to microbes in the first years of life

24
Q

What are Type II Hypersensitivities?

A

Antibody mediated (IgM or IgG); antibodies bind to the surface of cells or the ECM

25
Q

What are the means of destruction?

A

1) Antibody- dependent cell-mediated cytotoxicity (ADCC)
2) Complement system
3) Functional derangements

26
Q

Is ADCC complement dependent or complement independent?

A

Complement independent

27
Q

What types of cells are used in ADCC?

A

WBCs (monocytes, neutrophils, eosinophils, and NK cells) with Fc receptors that bind with IgG or IgM

28
Q

What immunoglobulins are good at fixing the complement?

A

IgM and IgG (Me Good and fixing complement!)

29
Q

What do products of complement proteins activate?

A

Macrophages and neutrophils

30
Q

What are functional derangements in Type II hypersensitivities?

A

Antibodies can act as agonists or antagonists to cell receptors. May occur with or without inflammation

31
Q

What are example of functional derangements in Type II hypersensitivities?

A

1) Myasthenia Gravis

2) Pernicious Anemia- antibodies react with intrinsic factor not permitting absorption of B12

32
Q

What do antibodies bind to in hemolytic anemias (Type II)?

A

Antibodies bind to carbohydrates or proteins present on RBCs and RBCs are phagocytized

33
Q

Briefly explain molecular mimicry (Type II).

A

Lymphocytes are activated by non-self that looks similar to self. Lymphocytes attack non-self and self. The BCRs and TCRs recognize one antigen.

34
Q

What is rheumatic heart disease (Type II)?

A

A streptococcal throat infection activates helper T cells. The helper T cells cross-react with a protein present on the mitral valve of the heart. The cross-reacting helper T cells direct an inflammatory attack on the heart

35
Q

What are Type III hypersensitivity reactions?

A

Antibody-antigen complexes accumulate, deposit in tissues and cause inflammation

36
Q

Where are antibodies and antigen complexes deposited?

A

Vascular walls (vasculitis) or other tissues (arthritis)

37
Q

What happens in Type III reactions?

A

1) IgM and IgG fix complement
2) Complement attracts neutrophils and macrophages
3) Fc receptors on neutrophils and macrophages bind the Fc regions of IgM and IgG
4) Phagocytes try to eat the antigen-antibody complexes and release inflammatory chemistry

38
Q

What is the inflammatory triad of cytokines?

A

IL-1, TNF, and IL-6

39
Q

What is lupus erythematosus (Type III)?

A

Inflammatory disease that mainly affect women. Targets the lungs, joints and kidneys. Due to a B and T cell intolerance

40
Q

What is the hallmark of Type III?

A

1) Deposition of antibody-antigen complexes
2) IgG and IgM
3) Phagocytes get attracted and cause inflammation

41
Q

What are Type IV hypersensitivities?

A

1) Delayed Type Hypersensitivity (DTH)

2) Cell mediated cytotoxicity

42
Q

Do Type IV Hypersensitivities involve antibodies?

A

No

43
Q

How are Type IV hypersensitivities stimulated?

A

1) Bacteria
2) Fungi
3) Viruses

44
Q

Explain Delayed Type Hypersensitivity.

A

1) Th1 cells secrete large amounts of INF-y

2) INF-y stimulates macrophages

45
Q

What cells do most of the damage in DTH?

A

Macrophages

46
Q

What do macrophages stimulate in DTH?

A

Stimulate fibroblasts leading to fibrosis

47
Q

What are examples of DTH?

A

1) Contact dermatitis
2) Crohn’s disease
3) Type I diabetes
4) MS

48
Q

How is multiple sclerosis activated (Type IV)?

A

Initiated by self reactive T cells

49
Q

What is the target of multiple sclerosis?

A

Myelin basic protein

50
Q

Explain Cell Mediated Cytotoxicity.

A

Killer T cells (CTL) kill cells displaying foreign antigens

51
Q

What do CTLs release in cell mediated cytotoxicity?

A

INF-y which activate macrophages

52
Q

What is a major reason why organ transplants are rejected?

A

Cell Mediated Cytotoxicity

53
Q

Give an example of cell mediated cytotoxicity besides rejection of organ transplants.

A

Viral hepatitis

Immunology Final (7 decks)

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