Immune system disorders
A. Hypersensitivities
Type I Hypersensitivity (allergy)
- First exposure to an allergen:
- TH2-stimulated overproduction
of IgE
- IgE binds to mast cells and basophils (sensitization)
- Second and later exposures to allergen
- allergen binds to IgE on mast cell
- Mast cell releases histamine, leukotriene
- Histamine effects
- Leukotriene effects
- Types of allergic reactions
- Anaphylactic shock
- Hay fever
- Asthma
- Food allergy: Peanuts,
shellfish
- Drug allergy: Penicillin
- Treatments
- Epinephrine
- Steroids
- Antihistamines
- Desensitization
Type II Hypersensitivity (Cytotoxic)
- Autoimmune Diseases
- Graves'
Disease
- IgG vs. TSH receptor = overstimulate thyroid
- Goodpasture's
Syndrome
- Transfusion reactions
- Hemolytic Disease of newborns
Type III Hypersensitivity (Immune
complex)
- Lupus (SLE)
- ANA (antinuclear antibodies) form
- Ab|Ag complexes deposited in capillaries
- Complexes trigger inflammation, activate complement
- Rheumatoid arthritis
- IgG formed vs. synovial membrane (lining of joints)
- Inflammatory response and release of TNF
Type IV Hypersensitivity (delayed
hypersensitivity)
- Exposure to antigen activates special TH1 cells called TDTH
cells
- TD cells proliferate = sensitization
- Second or continued exposure:
- TD migrate to area (slow; 24 - 48 hrs)
- activated
TD cells release cytokines
- Macrophages attracted
- Inflammation due to cytokines
- Examples
- Contact dermatitis: Poison Ivy, jewelry, latex
- Delayed transplant rejection
- TB skin test
- Chronic infectious disease damage (TB, leprosy, herpes)
- Type 1 diabetes mellitus
- Multiple sclerosis
B. Immune deficiencies
- B-cell deficiencies
- agammaglobulinemia (congenital)
- IgA deficiency (congenital)
- T-cell deficiencies
- Phagocyte deficiencies
- Chronic granulomatous disease
- Complement deficiencies
- Combined immunodeficiencies
- Neonates
- Passive protection by maternal IgG
- Insufficient T-cell responses (immature)
- increased severity of viral infection (Herpes)
- decreased severity of immunopathogenesis (measles)
Are T-cell deficiencies more serious than B-cell deficiencies?
C. Cytokine storm
- sepsis
- superantigens
D. autoimmunity
- Override Treg effect (excess cytokines)
- antigen cross-reaction
E. Immune system evasion by pathogens
- Bacteria
- evasion of phagocytosis
- complement inactivation
- antibody binding/destruction
- intracellular life
- antigenic variation
- Viruses
- Hidden from immune system (latency; syncytia)
- antigenic variation
- blocking antigens
- IFN suppression
- lymphocyte death or suppression
- IL-10 mimics
- MHC reduction
- cytokine effect block
- Parasites
- intracellular life
- inhibit phagocytic killing
- blocking antigens
- antigenic variation
- cysts
Links/References
- Peanut allergy: http://www.allerg.qc.ca/peanutallergy.htm
- Graves' Disease: http://www.bio.davidson.edu/Courses/Immunology/Students/Spring2003/Breedlove/GravesDisease.html
- Goodpasture's: http://kidney.niddk.nih.gov/kudiseases/pubs/goodpasture/
- Lupus: http://cerebel.com/lupus/overview.htm
- SCID; http://student.biology.arizona.edu/honors2000/group08/main.html