Allergy Flashcards
Basic Function of Immune System and its Role in Health and Disease
- protects us from pathogens
- many diseases are a result of immunodeficiency or autoimmune disease
Allergy=hypersensitivity
How our immune system responds to exposure to antigens
- hay fever
- granuloma formation during infection
TYPE 1 (Immediate) Hypersensitivity
An “allergic reaction,” develops within minutes of exposure to antigen
Manifestations range from hives to anaphylactic shock
Examples: Allergies, Anaphylaxis, Asthma
1. B cells activated by antigen
2. B cells turn into plasma cells, which make tons of IgE
3. Circulating IgE is taken up and displayed by mast cells
4. Antigen binds to Fab (arms) of IgE
5. Antigen dimerizes when binds, which causes a reaction with the cell
6. Degranulation
7. Elicit a range of local and systemic responses
The Mast Cell
Part of Type 1 Hypersensitivity
Specialized WBC found in tissue near blood vessels
Contain granules in cytoplasm filled with active mediators like histamine
Surface of mast cell has binding sites for Fc (feet) portion of IgE antibody (produced by B cells)
Histamine will cause edema and itching (hives) in the skin
-causes vascular dilation, so blood flow slows and they become leaky=edema
Asthma
Hypertrophy of goblet cells and muscle of bronchiole due to repeated constriction
Repeated episodes of T1 Hypersensitivity, structures in the lungs change which make asthma symptoms worse
Anaphylaxis
Hypotension due to widespread vascular leakage and decreased vasomotor tone
Respiratory distress due to bronchoconstriction or airway obstruction (so much mucus; hypoxia can cause death) due to laryngeal edema
Treat with epinephrine: relaxes airway muscles and increases BP (bronchodilation and vasoconstriction)
TYPE 2 (Antibody-mediated) Hypersensitivity
Immune reaction due to binding of antibodies to cell surface antigens
Examples: Autoimmune Hemolytic Anemia, Goodpasture syndrome-antibodies bind to basement membrane of lungs and kidneys- resp and renal failure follow due to compromise of air exchange and filtration capacities of respective organs
1. Antibody production
2. Antibody binds host tissue
3. Host tissue destruction
-Neutrophils are attracted to cells that are coated in antibody and avidly phagocytose them
-Natural Killer cells also recognize antibody coated cells and destroys them
-OR antibodies on a cell surface can activate the complement system, which is a set of proteins that punches holes into cells and destroys them
IgM
Antibody that circulates as a large molecule comprised of 5 individual IgM antibodies joined together as a pentamer.
Seen early in the antibody response to infection
IgG
primary antibody in antibody response to infection and appears soon after IgM. Circulates as a monomer
IgA
Distinctive because it is found in secretions and can be found on mucosal surfaces, in breast milk, and in saliva
IgE
Antibody associated with immediate (Type 1) hypersensitivity; found on surface of mast cells
IgD
Found on the surface of developing B cells as a receptor molecule
TYPE 3 (Immune Complex Mediated) Hypersensitivity
Complexes comprised of antibody bound to circulating proteins that contain the target antigen
These immune complexes can sometimes be deposited on blood vessel walls and in tissues; injury to vessel walls and tissues may ensue because of thrombosis and complement activation
Example: SLE or Lupus, Serum Sickness (horse serum), Arthus Reaction (skin necrosis)
Lupus: antibodies are directed against a variety of antigens found within the nucleus of our own cells; inflammation and cell damage releases these nuclear antigens and immune complexes form; the complexes are deposited in the kidneys, joints, and blood vessels resulting nephritis, arthritis, and vasculitis
TYPE 4 (cell mediated) Hypersensitivity
Initiated by T cells and is also called delayed type hypersensitivity
T cell response eliminates cells that are infected by intracellular pathogens
Takes 24-72 hrs to develop because T cells have to interrogate cells and calling macrophages to give selling, this takes time.
Examples: Contact Dermatitis (poison ivy), TB Infection, Transplant rejection
TB TEST
-in patients with prior sensitization to TB, redness and swelling around injection site
-this is due to vascular dilation and edema at the injection site mediated by T cells that were primed against the tuberculin during prior sensitization to TB.
T cells primed against foreign antigens can orchestrate an immune response against anything that displays the antigen
T cell response can elicit local inflammation that leads to a series of events that can either directly kill cells (cytotoxic) or activate macrophages to form granuloma and ingest antigen.
