immunology set 2.1

a person who is overly reactive to a substance that is tolerated by most other is said to be

hypersensitive (allergic)

whenever an allergic reaction occurs, there is...

tissues injury

antigens that induce an allergic reaction are

allergens

adverse reactions caused by immune mechanisms are termed

hypersensitive reactions

hypersensitivity

an exaggerated response by the immune system to a particular substance

primary mediator is the

adaptive imune system

damage is mediated by the same attack mechanisms that mediate...

normal immune responses to pathogens

the classification of Gell and Coombs divides hypersensitivity reactions into how many types?

4 (or 5) types

Gell and Coombs Classification: Types I, II, and III require...

the active production of antibody by plasma cells (terminally differentiated by B cells)

Gell and Coombs Classification: Types IV is mediated by

the interaction of T cells and macrophages

mechanisms of immune injury I, II, III, IV stands for

ABCD

Allergic Anaphylaxis & Atopy

antiBody

immune Complex

Delayed

What is a type I hypersensitivity reaction?

Allergic reaction mediated by IgE antibody

What is a type II hypersensitivity reaction?

cell mediated. IgG or IgM reacts with cell bound antigen. ex: ABO incompatibility, Rh, myasthenia gravis, ITP, Graves

What is a type III hypersensitivity reaction?

Type III hypersensitivity is an immune complex-mediated reaction in which an antigen-antibody complex lodges in tissue, activating complement, and attracting phagocytes that cause tissue damage

What is a type IV hypersensitivity reaction?

delayed type. antigen stimulation of previously sensitized T cells. TB skin test. poison ivy, contact dermatitis.

what is a type I hypersensitivity reaction mediated by?

IgE antibody, complement is not involved

what is a type II hypersensitivity reaction mediated by?

IgM or IgG ; complement

what is a type III hypersensitivity reaction mediated by?

IgG ; complement

what is a type IV hypersensitivity reaction mediated by?

cell-mediated anti-body-independent

which of the types of hypersensitivity Is the most common?

Type I (54%)

Type I hypersensitivity

occurs in atopic, within a few minutes after a person sensitize to an allergen is re-exposed to it. initial contact is asymptomatic

may be localized or systemic

Type I hypersensitivity occurs in response to: (2)

1. environmental allergens (pollen)

2. administered antigens (penicillin)

how is Type I Hypersensitivity triggered?

when an Ag binds to IgE Abs on the surface of mast cells and basophils; leads to degranulation and release of inflammatory mediators

process called cross-linking

the different symptoms of Type I Hypersensitive develop over minutes to hours are mainly due to...

the systemic effects of histamine release

where are mast cells located?

including the...?

in connective tissue

including the skin, the linings of the stomach and intestinal

what is an example of a chemical "alarm" a mast cells may release

histamine

by releasing chemical "alarms", mast cells attract other key players of the immune defense system to....

areas of the body where they are needed

what are other roles mast cells may have?

wound healing -> itching felt around a healing scab may be caused by histamine released by mast cells

growth of blood vessels

Type I Hypersensitivity treatment

EPINEPHRINE (Beta-adrenergics), antihistamines, corticosteroids, anticholinergics

vasoactive factors in S.1.H (4)

1. histamine

2. platelet-activating factor (PAF)

3. slow reacting substance of anaphylaxis (SRS-A)

4. prostaglandins and thromboxane

chemotactic factors in S.1.H (2)

1. neutrophil chemotactic factor (NCF)

2. eosinophil chemotactic factor of anaphylaxis (ECF-A)

effects of vasoactive/chemotactic factors (4)

1. increase vascular permeability (capillaries) which results in edema

2. causes smooth muscle contraction in bronchioles and small blood vessels

3. activate platelets

4. cause erythema

clinical examples:

1. allergic or atopic reactions (6)

1. seasonal rhinos (hay fever)

2. allergic asthma

3. urticaria (hives)

4. atopic dermatitis

5. allergic rhinitis

6. allergic conjunctivitis

clinical examples:

2. systemic anaphylaxis (anaphylactic shock)

is a potentially Fata reaction, characterized by the rapid onset of: urticaria bronchospasm, laryngeal edema and shock

after exposure to an offending antigen

what is the most common immunological abnormality seen in medical practice?

IgE mediated symptoms

type 1 hypersensitivity aka

anaphylactic, immediate

type II hypersensitivity aka

cytotoxic

type III hypersensitivity aka

immune complex disease

type IV hypersensitivity aka

cell-mediated, delayed

mechanism of type I hypersensitivity

antigen cross-links IgE on presensitized mast cells and basophils, triggering release of histamines

mechanism of type II hypersensitivity

IgM and IgG bind to antigen on "enemy" cell, leading to lysis by complement or phagocytosis

mechanism of type III hypersensitivity

antigen-antibody complexes activate complement, which attracts PMNs, which release lysosomal enzymes

mechanism of type IV hypersensitivity

sensitized T lymphocytes encounter Ag and release lymphokines, leading to macrophage activation

steps of type I hypersensitivity reaction?

when IgE meets is specific allergen,...

it causes the mast cell to discharge its contents of vasoactive substances into the circulation

atopy

hypersensitive or allergic state involving an inherited predisposition

____ is one of the most densely mast cell populated areas

conjunctiva

how many mast cells are in 1 eye

50 million

ADCC stands for

Antibody-dependent cell-mediated cytotoxicity

type II reactions re caused by __ or ___ directed against a person's ????

IgG or IgM

blood cells or tissue cells

type II hypersensitivy antigens involved are usually localized to...

tissue basement membranes or blood cell membranes

type II (_____) or _____ hypersensitivity

cytotoxic

subacute

ADCC involves the activation of

NK cells and eosinophils by antibodies

the reaction of antibodies and antigens of type II hypersensitivity usually leads to ___ and _____

phagocytosis and complement-mediated lysis of the cellular antigens

diagnostic tests of type II hypersensitivity includes (2)

1. detection of circulating antibody against the tissues involved

2. presence of antibody and complement in the lesion (biopsy) by immunofluorensce is linear in type II

type II is also called

Antibody-dependent cell-induced cytotoxicity (ADCC)

how long is the onset and duration of type II

1-3 hours for onset and long duration of 10-15 hours

role of NK cells in type II HS

Fc portion of the Ab molecule reacts with the Fc receptor of a variety of cytotoxic leukocyte, NKC most importantly

Ag involved in type II HS are usually localized to...

tissue basement membranes or blood cell membranes

Ag on the patient's own cell surfaces are recognized by ____ or ____ which act as APC