Page 119 - Concise Pathology for Exam Preparation ( PDFDrive )

104 SECTION I General Pathology

CD8+ T cells come in contact with antigen presenting target cells

Polymerization of perforin molecule

Insertion into target cell membrane

Drilling of holes in the membrane
Lymphocyte granules
Excessive water intake
contain granzymes

Delivered into the cell via
Osmotic lysis
perforin­induced pores

Fas–Fas ligand binding Apoptosis of target cells Granzymes cleave and activate
caspases to initiate apoptosis
FLOWCHART 5.9. T cell-mediated cytotoxicity/cytolysis.

Q. Tabulate differences between the different types of hypersensitivity.
Ans. Differences between types I, II, III and IV hypersensitivity are summarized in
Table 5.6.

TABLE 5.6. Differences between types I, II, III and IV hypersensitivity
Features Type I Type II Type III Type IV
Reaction type Anaphylactic Cytotoxic • Serum sickness Delayed hypersen-
• Arthus reaction sitivity

Cells involved Mast cells, basophils, Nonsensitized macro- Neutrophils, B cells CD41 T
cells, mac-
eosinophils, neutro- phages, NK cells, rophages, CD81
phils, monocytes, neutrophils, eosin- T cells
cells, B cells
CD41 T ophils, B cells
Antibody type IgE IgG, IgM IgG, IgM None
Chemical mediators IL-3, 4, 5; vasoactive Complement system Complement system Lymphokines,

amines IL-12, IL-2, INF-

g, TGF-b, TNF-
a
Antigen presenta- Required Not required Required Required
tion by APC
Pre-sensitization Required Not required Required Required
Pathogenesis Formation of IgE and Opsonization and Formation and depo- • Sensitized

immediate release of p h a g o c y t o s i s , sition of Ag–Ab T- lymphocytes
mediators to recruit ADCC, antirecep- complexes n acti- mediate release

inflammatory cells tor antibody type vates complement of lymphokines
inducing inflamma- system n neutro- • T cell-mediated

tory changes phils recruited n cytolysis

release of lyso-
somal enzymes and

other toxic agents

Time for onset Minutes Hours to days Hours to days Hours to days
Examples Allergic bronchial Transfusion haemo- Glomerulonephritis, Transplant rejection
asthma lytic reactions rheumatoid arthritis
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