MidTerm
Hypersensitivity: Type 1 - Correct Answer Type 1: Allergic reaction, Mediated by IgE,
Inflammation due to mast cell degranulation
Local symptoms:
-itching
-rash
Systemic symptoms:
-wheezing
Most dangerous = anaphylactic reaction
systemic response of hypotension, severe bronchoconstriction
Main treatment: epinephrine reverses the effects
Hypersensitivity: Type 2 - Correct Answer Type 2: Cytotoxic reaction; tissue specific
(ex: thyroid tissue)
Macrophages are the primary effectors cells involved
Can cause tissue damage or alter function
Grave's disease (hyperthyroidism) - example of altering thyroid function, but does not
destroy thyroid tissue
Incompatible blood type- example of cell/tissue damage that occurs; severe
transfusion reaction occurs and the transfused erythrocytes are destroyed by
agglutination or complement-mediated lysis.
Type 1 Hypersensitivity VS. Type 2 Hypersensitivity - Correct Answer Type 1
Hypersensitivity
Organ Specific
Antibody binds to the antigen on the cell surface
Type 2 Hypersensitivity
Not Organ Specific
Antibody binds to the soluble antigen outside the cell surface that was released into
the blood or body fluids, and the complex is then deposited in the tissues
Hypersensitivity: Type 3 - Examples - Correct Answer Rheumatoid arthritis:
Antigen/antibodies are deposited in the joints
Systemic Lupus Erythematosus (SLE)- very closely related to autoimmunity-
antigen/antibodies deposit in organs that cause tissue damage
Hypersensitivity: Type 4 - Correct Answer Delayed response
, Does not involve antigen/antibody complexes like Types 1, 2 and 3
Is T-cell mediated
Differentiating Between the Rash of a Type 1 vs. Type 4 Reaction: - Correct Answer
Type 1: Immediate hypersensitivity reactions, termed atopic dermatitis, are usually
characterized by widely distributed lesions
Type 4: Contact dermatitis (delayed hypersensitivity) consists of lesions only at the
site of contact with the allergen
The key determinant is the timing of the rash:
-Type 1 = Immediate
-Type 4 = Delayed: Several days following contact, ex would be poison ivy
Treatment of Type 4 Rash - Correct Answer A non-severe case of contact dermatitis
would be treated with topical corticosteroid.
Why not epinephrine or antihistamines?
-Epinephrine is for emergent Type 1 anaphylactic reactions. Antihistamines act on
the H1 receptors. Type 4 does not involve mast cells and H1 receptors.
Antibiotics not appropriate since not an infection
Autoimmunity - Correct Answer Autoimmune disease can be familial, Affected family
members may not all develop the same disease, but several members may have
different disorders characterized by a variety of hypersensitivity reactions, These
include autoimmune and allergic reactions
Associations with particular autoimmune diseases have been identified for a variety
of major histocompatibility complex (MHC) alleles or non-MHC genes
Alloimmunity - Correct Answer General term used to describe when an individual's
immune system reacts against antigens on the tissues of other members of the
same species.
Examples: Neonatal disease where the maternal immune system becomes
sensitized against antigens expressed by the fetus, Transplant rejection, Transfusion
reaction
Primary Immunodeficiency - Correct Answer Most primary immune deficiencies are
result of single gene defects
Something is lacking with the immune system itself.
Example: B-lymphocyte deficiency - one of the most severe forms of a primary
immunodeficiency
Secondary Immunodeficiency - Correct Answer Complication of some other
physiological condition/disease, Malnutrition one of most common causes worldwide.
Example: Pt. with HIV gets pneumocystis carinii