Type-IV Hypersensitivity Reaction

Dr. Arushi Agarwal

JR-1Pathology

Hypersensitivity ReactionInjurious immune response

Exaggerated/inappropriate state of normal immune response with onset of adverse effects on the body

TypesImmediate type

Type I : Anaphylactic Type II : Cytotoxic Type III : Immune Complex Mediated

Delayed Type Type IV : Cell-Mediated

Type IV Hypersensitivity

Cell-mediated immune disorders

Caused by: Cytokines produced by CD4+T cells

Cell killing by CD8+ T cells

Activation of CD4+T cellsCD4+T cells

Recognise peptides displayed by dendritic cells

Secrete IL-2

Proliferation of antigen-responsive T cells

Differentiation of antigen responsive T-cells

Antigen presenting cells

TH17 SUBSET(Dominated by neutrophils)

TH1 SUBSET(Dominated by activated macrophages)

IL-12 IL-2, IL-3, IL-23

Examples:• Tuberculin reactions• Granulomatous

inflammation• Contact dermatitis • Rheumatoid arthritis

• Multiple sclerosis• Inflammatory Bowel

Disease• Psoriasis

T-cell mediated killing of targets involves:

• Perforins and granzymes

• Activation of apoptosis.

• Examples: Type 1 Diabetes Mellitus

Thank you