Download Kuby Immunology 6/e

Hypersensitivity
Reactions type IV
PhD. student kefah F.Hasson
2014
Characteristics
 Interaction of primed T cells and associated antigen

Involve reactions by T memory cells.

Reactions are delayed by one or more days (delayed
type hypersensitivity -DTH) .
Infiltration of Mononuclear Cells ( Inflammatory
response).

Delayed is relative because DTH response arise 2472 hours after exposure rather than within minutes.
 Delay is due to migration of macrophages and T cells to
site of foreign antigens.

Reactions are frequently displayed on the skin:
itching, reddness, swelling, pain
Mechanism of type IV hypersensitivity
1) Inflammation and tissue injury mediated
by CD4+Th1.
Immune injury mainly caused by infiltration of
mononuclear cells and lymphocytes , release
cytokines .
2) Cytotoxicity of CD8+CTL
BACTERIA
M.tuberculosis
Brucella abortus
Listeria monocytogen

Virus
Measles
Herpes simplex

Fungus
Histoplasma
Candida
 protozoa
Leishmania
 Others

Ivy poison
Hairs dye
Metals poison
Nickel salts
INTRACELLULAR PATHOGENS
INDUCE DELAYED TYPE
Effector phase
Diseases of Type IV (Cell-Mediated) :
1) Infectious delayed type hypersensitivity like :
OT( Old Tuberculin ) test.
2) Contact dermatitis :like water blister .
3) Acute rejection of allogenic
transplantation .
Allergic Contact Dermatitis Response to
Poison Ivy
Granuloma Formation from DTH
Mediated by Chronic Inflammation
Four types of Hypersensitivity Reactions
Type II
Type I
Ag
Y
IgE
Y
Target cell
IgG
Target
Fc receptor cell
Complement
Ab
Neutrophils
Endothelial cells
Fc recepKiller cell
Mast cells
tor
Ab
Histamine
Complement
Type III
Type IV
Ag
Ag
Th
Macrophage
Th
cell
Cytokines
Activated Macrophage
Topic for exam
The Gall & Coombs classification of
hypersensivity reactions .
 Type I ,II ,III ,IV hypersensivity reactions
mechanism & example .
 Immunological basis of the HDN caused
by Rh incompatibility .
 Mention the common diseases of each
types of hypersensivity reactions.
