Ch'19 Hypersensitivity Reactions

1
Ch.19 Hypersensitivity Reactions

• Response to antigens (allergens) leading to
  damage
• Require sensitizing dose(s)
• Four types of hypersensitivity reactions

2
Type I (Anaphylactic) Reactions

• Involve IgE antibodies
• Localized Hives or asthma from contact or
  inhaled antigens
• Systemic Shock from ingested or injected antigens

Figure 19.1a
3
Type I (Anaphylactic) Reactions

• Skin testing
• Desensitization

Figure 19.3
4
Type II (Cytotoxic) Reactions

• Involve IgG or IgM antibodies and complement
• Complement activation causes cell lysis or damage
  by macrophages

5
ABO Blood Group System
Table 19.2
6
Hemolytic Disease of the Newborn
Figure 19.4
7
Drug-induced Thrombocytopenic Purpura
Figure 19.5
8
Type III (Immune Complex) Reactions
Figure 19.6

• IgG antibodies and antigens form complexes that
  lodge in basement membranes.

9
Type IV (Cell-Mediated) Reactions

• Delayed-type hypersensitivities due to TD cells
• Cytokines attract macrophages and initiate tissue
  damage

Figure 19.8