Immunologic Disorders
What are the three types of immunologic disorders? - Hypersensitivity, immunodeficiency, and
autoimmunity.
What is an hypersensitivity immunologic disorders?
Definition - It's an overreaction by the immune system.
What is an immunodeficiency immunologic disorders?
Definition - When there is a weak or no immune system.
What is an autoimmunity immunologic disorders?
Definition - When the immune system attacks the host's own cells.
Terms related to hypersensitivities - Allergen: an antigen that is typically harmless, non-disease causing
substance from the environment but which triggers an immune reaction.
Sensitization: readiness for a severe secondary immune response.
Systemic anaphylaxis: the antigen spreads in the blood and blinds IgE on basophils which then release
inflammatory mediators (esp. histamine) which dilate vessels causing loss of fluids into tissues and
swelling. The blood pressure drops very low. The heart may fail. The brain and other organs become
oxygen-starved due to low blood pressure. Constriction of bronchi and swelling in the throat can
suffocate. Death is often rapid.
What are the four types of hypersensitive reactions? - Type 1 - "Immediate"; IgE-mediated
Type 2 - Cytotoxic
Type 3 - "Immune"; complex-mediated
Type 4 - "Delayed"; type; cell-mediated
, Features of Type 1 hypersensitive reactions: - Rapid-often 30 minutes or less; in the presence of the Ag,
B cells produce IgE which bind to mast cells which then produce excess histamine, etc.; blood vessels
leak; smooth muscles contract; usually causes a skin reaction.
What are causes of Type 1 hypersensitive reactions? - Pollen, venoms (bee stings; insect, spider, and
snake bites); food and antibiotic allergies; molds; pet dander.
What are results of Type 1 hypersensitive reactions? - Hives (wheal and flare); itching; runny nose,
watery eyes; hay fever; asthma; initial exposure sensitizes; more severe on subsequent exposure.
Worst case: systemic anaphylaxis!
Figure 17.1
Know in a general way - Exposure to allergens.
Figure 17.2 - Hives (wheal and flare).
Figure 17.3 - Desensitization against plant allergens for hay fever sufferers.
Features of Type 2 hypersensitive reactions. - Slow-hours or day; cellular Ag--RBCs; B cells produce IgG
and IgM; RBCs clump; complement is activated; MAC and NK cells attack RBCs; no skin reaction.
What is the cause of Type 2 hypersensitive reactions? - Transfusions of wrong blood type involving
either ABO or Rh factors.
What is the result of Type 2 hypersensitive reactions? - Blood incompatibility reaction; RBCs clump and
die; kidney damage; hemolytic disease of newborns.
ABO blood types: Ab agglutinates RBCs and blocks blood flow in vessels; reduced blood flow reduces
oxygen supply to tissues and reduces ATP for cellular transport; MAC of CS kills RBCs as in IIR. Ab tags
RBCs alerting NK cells to kill RBCs as in AIR.
What are the three types of immunologic disorders? - Hypersensitivity, immunodeficiency, and
autoimmunity.
What is an hypersensitivity immunologic disorders?
Definition - It's an overreaction by the immune system.
What is an immunodeficiency immunologic disorders?
Definition - When there is a weak or no immune system.
What is an autoimmunity immunologic disorders?
Definition - When the immune system attacks the host's own cells.
Terms related to hypersensitivities - Allergen: an antigen that is typically harmless, non-disease causing
substance from the environment but which triggers an immune reaction.
Sensitization: readiness for a severe secondary immune response.
Systemic anaphylaxis: the antigen spreads in the blood and blinds IgE on basophils which then release
inflammatory mediators (esp. histamine) which dilate vessels causing loss of fluids into tissues and
swelling. The blood pressure drops very low. The heart may fail. The brain and other organs become
oxygen-starved due to low blood pressure. Constriction of bronchi and swelling in the throat can
suffocate. Death is often rapid.
What are the four types of hypersensitive reactions? - Type 1 - "Immediate"; IgE-mediated
Type 2 - Cytotoxic
Type 3 - "Immune"; complex-mediated
Type 4 - "Delayed"; type; cell-mediated
, Features of Type 1 hypersensitive reactions: - Rapid-often 30 minutes or less; in the presence of the Ag,
B cells produce IgE which bind to mast cells which then produce excess histamine, etc.; blood vessels
leak; smooth muscles contract; usually causes a skin reaction.
What are causes of Type 1 hypersensitive reactions? - Pollen, venoms (bee stings; insect, spider, and
snake bites); food and antibiotic allergies; molds; pet dander.
What are results of Type 1 hypersensitive reactions? - Hives (wheal and flare); itching; runny nose,
watery eyes; hay fever; asthma; initial exposure sensitizes; more severe on subsequent exposure.
Worst case: systemic anaphylaxis!
Figure 17.1
Know in a general way - Exposure to allergens.
Figure 17.2 - Hives (wheal and flare).
Figure 17.3 - Desensitization against plant allergens for hay fever sufferers.
Features of Type 2 hypersensitive reactions. - Slow-hours or day; cellular Ag--RBCs; B cells produce IgG
and IgM; RBCs clump; complement is activated; MAC and NK cells attack RBCs; no skin reaction.
What is the cause of Type 2 hypersensitive reactions? - Transfusions of wrong blood type involving
either ABO or Rh factors.
What is the result of Type 2 hypersensitive reactions? - Blood incompatibility reaction; RBCs clump and
die; kidney damage; hemolytic disease of newborns.
ABO blood types: Ab agglutinates RBCs and blocks blood flow in vessels; reduced blood flow reduces
oxygen supply to tissues and reduces ATP for cellular transport; MAC of CS kills RBCs as in IIR. Ab tags
RBCs alerting NK cells to kill RBCs as in AIR.
