Hypersensitivity Hypersensitivity Reactions type Reactions type IVIV
PhD. student kefah F.Hasson2014
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 24-72 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
INTRACELLULAR PATHOGENS INTRACELLULAR PATHOGENS INDUCE DELAYED TYPE INDUCE DELAYED TYPE
BACTERIAM.tuberculosisBrucella abortusListeria monocytogen
VirusMeaslesHerpes simplex
FungusHistoplasmaCandidaprotozoaLeishmaniaOthersIvy poisonHairs dyeMetals poisonNickel salts
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 Allergic Contact Dermatitis Response to Poison IvyPoison Ivy
Granuloma Formation from DTHGranuloma Formation from DTH Mediated by Chronic Inflammation Mediated by Chronic Inflammation
Four types of Hypersensitivity ReactionsFour types of Hypersensitivity Reactions
YY IgE
Fc recep-tor
Histamine
Mast cells
Type I Type II
Type III Type IV
YY IgG
Killer cellFc receptor
Target cell
YAb
Complement
Target cell
Y
Y
Y
Y
ComplementAg
Ab
NeutrophilsCytokines
Th cell
Th
Macrophage
Activated MacrophageEnd
othe
lial
cel
lsAg
Ag
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