Hypersensitivities Flashcards
hypersensitvity
- altered immunologic response to an antigen
- results in disease/damage to host
- inappropriate activation of the immune system
requirements for hypersensitivity
- have to be genetically predisposed
- initial exposure alters immunologic homeostasis
Type I hypersensitivity
immediate/IgE mediated
Type II hypersensitivity
cytotoxic/tissue-specific
Type III hypersensitivity
immune complex mediated
Type IV hypersensitivity
delayed/cell mediated
hypersensitivity by immune mechanism:
antibody mediated
- Type I
- Type II
- Type III
hypersensitivity by immune mechanism:
cell mediated
-Type IV (only one not involving antibodies)
hypersensitivity by antigen:
allergy
environmental antigens, not “self”
hypersensitivity by antigen:
autoimmunity
self-antigens
hypersensitivity by antigen:
alloimmunity
“other” antigens; tissue of same species, not self (transplant)
hypersensitivity by speed of response:
immediate
- minutes to hours
- antibody mediated (Types I, II, and III)
- anaphylaxis
hypersensitivity by speed of response:
delayed
-hours to days cell mediated (Type IV)
Type I Hypersensitivity:
- _____ antigens
- _____ mediated, bound to ____
- 2nd exposure activates _____
- antigen _____
- mast cell _____, secondary to ____, releases _____
- mast cell initiates _____
environmental; IgE; Fc receptors; mast cells; cross links adjacent IgE; degranulates; Fc structure change; vasoactive substances; cytokine synthesis
Type I Hypersensitivity symptoms
- pruritus
- angioedema
- urticaria
- conjunctivitis
- rhinitis
- hypotension
- bronchospasm
- dysrhythmias
- GI cramps and malabsorption
Type I Hypersensitivity:
IgE mediated chronic diseases
- allergic asthma
- chronic urticaria
- eczema
Type I Hypersensitivity treatment
- desensitization
- tolerance
Type I Hypersensitivity:
desensitization
- increases threshold
- still allregic
Type I Hypersensitivity:
tolerance
- long-term immunologic change
- no longer allergic
anaphylaxis:
- Type _____ hypersensitivity reaction
- due to _____
- mildly sensitized: _____
- severely sensitized: _____
I;
widespread degranulation of mast cells;
mild reactions (itching, hives, skin erythema, contraction of respiratory bronchioles);
sever reactions (laryngeal edema, vascular collapse, death)
most common cause of death from anaphylaxis and how does it happen?
hypotension;
inflammation in vessels causes vasodilation and increased permeability, blood leaves vascular compartment and enters interstitial fluid –> hypovolemic shock, blood pressure decreases and heart rate increases
how does EpiPen work?
- epinephrine injection
- constricts blood vessels (raises blood pressure)
- relaxes smooth muscles (improves breathing)
- stimulates heartbeat
- reduces swelling
Type II Hypersensitivity:
- _____ mediated diseases
- abnormal production of ____
- ____ mechanisms
tissue-specific antibody;
IgM or IgG directed against antigens on specific tissues/cells;
5
5 mechanisms of Type II Hypersensitivity
1) complement-mediated lysis
2) opsonization and phagocytosis
3) neutrophil-mediated damage
4) antibody dependent cell mediated cytotoxicity
5) induced cell malfunction
Type II Hypersensitivity:
1) complement-mediated lysis
- complement system classical pathway is activated
- IgM or IgG bind to antibodies and membrane attack complex attack self cells
- ex: hemolytic disease of the newborn
Type II Hypersensitivity:
2) opsonization and phagocytosis
- C3b (product of complement system) opsonizes self-cell
- cell is phagocytosed
Type II Hypersensitivity:
3) neutrophil-mediated damage
- antigen deposits in tissue
- antibody binds
- complement activated
- neutrophil chemotaxis
- neutrophil adherence and degranulation
- result: some tissue damage and cell death
Type II Hypersensitivity:
4) antibody dependent cell mediated cytotoxicity
- natural killer cells have crystalline fragment receptors on them to recognize antibodies on cells
- natural killer cells release perforin and granzymes to destroy target cell\
- can play a role in transplant rejection
Type II Hypersensitivity:
5) induced cell malfunction
- causes increase or decrease in normal cell activity
- antibodies attack self = change the function
- problematic for cells that need to turn on and off or have feedback loop (ex: muscle cells, thyroid glands)
- this process is NOT cytotoxic
Type II Hypersensitivity:
5) induced cell malfunction examples
- Myasthenia gravis
- Grave’s disease
Myasthenia gravis
- antibodies block ACh receptors on muscle cell at neuromuscular junction
- prevents ACh released at motor end plate from activating muscle cell
- lid droop, double vision, weak grip, trouble swallowing/speaking, easily fatigued
Grave’s disease
- antibodies stimulate thyroid cells to overproduce thyroid hormone
- hyperthyroid
- goiter, increased metabolism, CNS effects (irritability), weight loss
- lid retraction - “thyroid stare”
- increased sympathetic activity
Type III Hypersensitivity:
- _____ mediated
- _____ complexes
- _____ antibodies
- complexes formed ____ and _____ in vessel walls or extravascular tissues
immune complex; antigen-antibody; IgG, IgM; in the circulation; deposited
Type III Hypersensitivity: immune complex clearance: large: \_\_\_\_\_ small: \_\_\_\_\_ intermediate: \_\_\_\_\_
macrophages;
renal clearance;
deposit in tissues
Type III Hypersensitivity:
systemic
- serum sickness
- Raynaud’s phenomenon
Type III Hypersensitivity:
localized
-arthus reaction (usually from an injection)
Type III Hypersensitivity:
immune complex-mediated diseases
- infectious (poststreptococcal glomerulonephritis, polyarteritis nodosa, reactive arthritis)
- autoimmune (lupus, rheumatoid arthritis, Sjogren’s, reactive arthritis)
Type III Hypersensitivity:
ocular manifestations of immune complex-mediated autoimmune diseases
- uveitis
- retinal vasculitis
- ischemic optic neuropathy
- scleritis
- peripheral ulcerative keratitis
- keratoconjunctivitis sicca
Type IV Hypersensitivity:
- mediated by _____
- direct action= _____
- indirect action= _____
- _____ response
- cells _____
T lymphocytes; cytotoxic T-cells; Th1 helper T-cells via activation of phagocytes (macrophages)- "coordinating the attack"; delayed; killing cells
Type IV Hypersensitivity:
- PPD skin test (TB skin test)
- read ____
- positive presents _____
- reaction caused by ____, NOT ____
between 48 and 75 hours;
a number of ways based on risk factors;
T-cells;
TB antibodies (although you may have them)
Type IV Hypersensitivity:
cell-mediated diseases
- environmental (contact dermatitis, Stevens-Johnson syndrome)
- TB-type (PPD reaction)
- autoimmune (Crohn’s, MS, T1 diabetes)
Type IV Hypersensitivity:
ocular manifestations
- uveitis, episcleritis, scleritis (Crohn’s)
- optic neuritis (MS)
- hemorrhagic conjunctivitis (Stevens-Johnson syndrome)
allergy:
- ____ antigens
- requires _____
environmental;
sensitization
most allergies are Type ___
I
allergy Type I:
- _____ hypersensitivity
- symptoms match _____
- higher ____ in general in people who are “atopic”
- genetically _____
immediate;
site of exposure (inhaled, ingested, exposed);
IgE titers and mast cells;
predisposed
allergic conjunctivitis:
- most exposed _____
- most densely ____
- ____ mediated
- type ___
mucous membrane;
mast cell populated areas;
IgE;
I
allergy Type II:
- usually against ____
- elicit ____ response
- example: ____
haptens that bind to the surface of cells;
IgG or IgM;
penicillin allergy
allergy Type III:
- ____ formation in response to environmental, soluble antigens
- example: _____
immune complex;
farmer’s lung
allergy Type IV:
- mostly ____, which need ____
- _____ mediated response
- example: _____
haptens;
carrier (usually proteins found in skin);
cell;
contact dermatitis
