Inflammation and Hypersensitivity Flashcards
The process by which the body attempts to destroy or contain a noxious agent and repair damage
Inflammation
What are the four phases of immune-mediated inflammatory responses?
- ) Stimulation
- ) Release of inflammatory mediators and chemotactic agents
- ) Invasion of tissue
- ) Removal of cell debris and secretion of growth factors
Which can act locally or systemically, and the response of local or distant target organs to them
Inflammatory mediators
Attract immune cells to the area and modify endothelium to allow their adhesion and extravasion
Chemotactic agents
The invasion of tissue is by activated immune cells which defend against infection and can also
Damage tissue
Stimulate cell migration and proliferation, with tissue repair and formation of new blood vessels
Growth factors
In acute local inflammation, inflammatory mediators produce which 4 things?
- ) Heat and redness
- ) Edema
- ) Pain
- ) Loss of function
The heat and redness is from
Dilation of small blood vessels
From endothelial retraction and increase in permeability of post-capillary venules
-causes fluid to leak from blood to tissue
Edema
Cytokines with systemic effects are chiefly produced by
Monocytes
Shape the systemic response of the body to infection, and produce many signs and symptoms by which illness is recognized
TNF-a, IL-1, and IL-6
Overproduction of inflammatory cytokines can produce the
Systemic Inflammatory Response Syndrome [SIRS]
Leads to loss of blood volume, and vasodilation, with decreased blood pressure and tissue perfusion, can lead to organ dysfunction, shock, and death
Increased Vascular Permeability
Severe shock produced by systemic infection is called
Septic shock
Bacterial components such as LPS activate the
Blood clotting cascade
Inflammatory cytokines act on endothelium to promote
Blood clotting
Multiplication of bacteria in the bloodstream [septicemia] can lead to
Disseminated Intravascular Coagulation [DIC]
Exhaustion of clotting factors by DIC can lead to simultaneous
Multiple hemorrhages
In chronic inflammation, persistent reactions to a stimulus that cannot be removed results in formation of a
Granuloma
A lesion with a necrotic core surrounded by macrophages and lymphocytes
Granuloma
On a longer time scale the granuloma becomes surrounded by fibrous tissue, to wall off the lesion. Eventually the wall of the lesion may
Calcify
Immune responses which damage the body
Hypersensitivity reactions
The immune system may over-react to an innocuous antigen [allergy]. The antigen is the
Allergen
A genetically-determined state of abnormal responsiveness is called
Atopy
An atopic person is not allergic until exposure to an allergen generates an
-may require months or years of exposure
Immune response
Classified by the mechanism that causes damage
Hypersensitivity reactions
Immediate hypersensitivity because the early phase happens so rapidly
Type I
Delayed or tuberculin-type hypersensitivity, because a classic stimulus is tuberculin, an extract of cultures of the bacterium which causes TB
Type IV
In responses of types I-III The antigen-specific component is
Immunoglobin
In responses of types I-III The antigen-specific component is immunoglobulin, and hypersensitivity can be transferred to an unsensitized individual with
Serum
Type IV antigen sensitivity is conferred by
-antibodies play no significant role
T cells
There are several subtypes of Type IV reactions: (1) granulomatous reactions, where the major cells are
TH and monocyte macrophages
There are several subtypes of Type IV reactions: (2) cytotoxic reactions, in which the important cells are
TH and CTL
Hypersensitivity reactions are used diagnostically. Small, localized, skin reactions are induced as tests of
Immune system competence, prior exposure, and allergic hypersensitivity
Anaphylactic hypersensitivity based on IgE and mast cells
Type I reactions
Opposite of prophylaxis; deleterious effects of exposure to antigen, as opposed to the beneficial effect of immunization
Anaphylaxis
The basis of a type I reaction is the
Synthesis of IgE and antigen-stimulated degranulation of mast cells
Binds tightly and specifically to Fc receptors [FCR] on mast cells
IgE
Cross-linking of cell-bound IgE by polyvalent antigen causes release of
Mast cell granule contents
Microbial polysaccharides or immune complexes containing IgG/IgM also stimulate mast cells via activation of
Complement
This occurs directly by alternate pathway, or by classical pathway in the presence of
IgG/IgM
Peptides generated by Complement activation bind to mast-cell receptors, again cause
Degranulation
Stimulated mast cells release
Inflammatory Mediators
Made prior to simulation, stored in mast cell granules, released on degranulation
Pre-formed mediators
Causes airway smooth muscle contraction, dilation of small blood vessels, increased permeability of post-capillary venules, and secretion of mucus by the nasal mucosa
Histamine
Acts by binding to several types of G-protein coupled receptors on target cells
Histamine
Occupy these receptors but do not activate the target cells, i.e. they are receptor antagonists
Antihistamines
Contraction of bronchial smooth muscle in response to mast cell products is one basis of
Allergic asthma
Synthesized and released after mast cell stimulation
Lipid mediators
Derived from C20 cell-membrane lipids
Prostaglandins and Leukotrienes
Before the identity of mast-cell prostaglandins/leukotrienes was known they were referred to as the
Slow-Reacting Substance of Anaphylaxis [SRS-A]
Defends us against tissue parasites
IgE/Mast cell system
Stimulated mast cells release the protein
Esosinophil Chemotactic Factor A (ECFA)
A chemoattractant for eosinophils
ECFA
Type II reactions are classified as
Cytotoxic hypersensitivity
Antibody binds to specific antigen on cell surface, causing destruction by Complement or phagocytosis in
Cytotoxic hypersensitivity (Type II reaction)
The antibodies responsible for type II reactions are mostly
IgG or IgM
Bound IgG antibody facilitates
Phagocytosis (opsonization)
Bound IgG antibody facilitates phagocytosis (opsonization) because phagocytes have membrane receptors
FCRy for its Fc region
Transfusion of mismatched blood is an example of a
Type II reaction
Fetal hemolytic disease arising from Rh incompatibility between mother and fetus is an example of a
Type II reaction
What are two other examples of type II reactions?
Hyperacute rejection of organ transplant and some drug allergies
Binds to red cell proteins, acts as a hapten, and stimulate formation of antibodies that then lyse drug-coated red cells
Penicillin
Type II reactions are classified as
Immune complex diseases
In a type II reaction, the reaction of antigen with antibody [especially in antigen excess] forms soluble
Immune complexes
These complexes can cause
Arthritis, glomeronephritis, and vasculitis
What are four examples of type III reactions?
- ) Pulmonary reactions
- ) Arthus reaction
- ) Autoimmune diseases
- ) Serum sickness
Pulmonary reactions to inhaled antigens is the basis of many occupationally-related disease, such as Farmer’s lung. The antigens responsible are often
Fungal
Arises from reaction to fungal spores in moldy hay
Farmer’s lung
Experimental administration of soluble antigen to an immune subject results in a skin lesion redness, and swelling
-takes 3-8 hours to develop].
Arthus reaction
Rheumatoid Arthritis is an example of a
Type III reaction
In RA, the antigen is
IgG
Autoantibodies are made to many cell components including DNA, RNA, nucleoproteins in
Systemic Lupus erythematosis
Caused by repeated administration of non-human serum, for example injection of equine antiserum for snakebite in a person who had received horse serum before
Serum sickness
Type IV reactions are called
Cell mediated
Antigen specificity for type IV reactions is provided by
CD4+ TH cells
Antigen specificity is provided by CD4+ TH cells, on stimulation they release cytokines/chemokines, infiltration of the site by
Macrophages and CTL
Classic Type IV skin reactions are characterized by
Induration and erythema
Hardness, from cell infiltration
Induration
Require 48-72 hours to develop
Class IV skin reactions
Skin response to a panel of common antigens is used diagnostically to assess competence of
Cell-mediated immunity
Class IV skin reactions are often called
Tuberculin-type reactions
Form at sites infected by microbes that survive/multiply inside cells
Granulomatas
Granulomas form at sites infected by microbes that survive/multiply inside cells. The classic cause is
Mycobacterium tuberculosis
Follows exposure to poison ivy or chemicals such as chromate salts or metals
Contact hypersensitivity dermatitis
Allergens bind to cell surface proteins, act as haptens, and stimulate
Cell-mediated immunity
Like tuberculin reactions, they develop in 2-3 days
Contact hypersensitivity dermatitis
Acute rejection of organ transplants. Requires weeks/months and involves both
CD4+ and CD8+ cells
Takes months or years and the mechanism is obscure; possibly fibrosis in response to cytokine release
Chronic rejection