OTH3416 Ch. 7 questions with complete solutions

OTH3416 Ch. 7 questions with
complete solutions

Hypersensitivity - ANS ✔✔• Sometimes normally functioning immune responses are not
advantageous

• These inappropriate immune responses are referred to as hypersensitivity, which is
characterized by the immune system destroying healthy tissues\cells

1. Allergic reaction occurs when the immune system overreacts (is hypersensitive) to
noninfectious environmental antigens

2. Autoimmune disease occurs when the immune system attacks the person's own cells and
tissues

3. Alloimmune response occurs when transplanted organs or blood cells (blood transfusion)
from a donor are rejected because they are recognized as non-host cells



Hypersensitivity Reactions - ANS ✔✔• This inappropriate hypersensitivity reaction always takes
place after re-exposureto an antigen, not immediately

• Hypersensitivity reactions are either:

1. Immediate: minutes to hours after re-exposure, or

2. Delayed: hours to days after re-exposure

• All hypersensitivities may be life threatening



Classification of Hypersensitivity Reactions - ANS ✔✔• Hypersensitivity reactions are classified
in two different ways:

1. According to the stimulus (3 types):

a. Allergy: exaggerated immune response against allergens(environmental antigens, non-
infectious)

b. Autoimmunity: misdirected immune response against the host's own cells

, c. Alloimmunity:immune response against beneficial foreign tissue (transplanted tissue/organ or
blood transfusion)

2. According to the type of reaction (4 types) a. Type I: IgE-mediated

b. Type II: tissue-specific reactions

c. Type III: immune-complex mediated

d. Type IV: cell-mediated reactions



4 types of Hypersensitivity Reactions - ANS ✔✔• The four types of hypersensitivity reactions
(may be allergies, autoimmunity or alloimmunity):

- Type I: IgE-mediated allergic reactions (e.g., seasonal allergic rhinitis), mast cells are activated

- Type II: tissue-specific reactions, allergy, autoimmune, and alloimmune; macrophages \ NK
cells are activated

- Type III: immune-complex-mediated reactions -autoimmune disease (e.g., systemic lupus
erythematosus); neutrophils are activated

- Type IV: cell-mediated reactions, allergy, autoimmune, and alloimmune (e.g., poison ivy); T-
cells&macrophages

• Types I, II, and III are mediated by antibodies, while type IV is mediated by T lymphocytes

• Upon re-exposure, Types I, II, and III are immediate while type IV is delayed



Allergies - ANS ✔✔• Allergies are the most common and the least life threatening of all
hypersensitivity reactions

• Introduced in four possible ways:

a. Skin contact

b. Injection

c. Ingestion

d. Inhalation

• Most allergens are small proteins

• Typical allergens: