Hypersensitivity Type I, II, III and IV- Summary in table form

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Hypersensitivity (also known as hypersensitivity response or intolerance) is a term used to describe undesirable reactions that are caused by the immune system, which includes autoimmunity and allergies. These are typically called an overreaction of the immune system, and these reactions can be harmful and uncomfortable. It is an immunologic term , and should not be misinterpreted as a psychiatric term of being hypersensitive, which refers that a person is hypersensitive to physical (ie sounds, touch light, sound, etc.) or emotional stimuli. However, there is a link between the two , studies have demonstrated that with ADHD (a mental disorders) tend to experience hypersensitivity reactions, such as asthma, allergies, or eczema and more than people who don’t have ADHD.

Different kinds of hypersensitivity reactions

The hypersensitivity reaction can be divided into 4 different types.

  • Type I: IgE mediated immediate reaction
  • Type II: The antibody-mediated Cytotoxic Reaction (IgG or IgM antibodies)
  • Type III: Complex-mediated immune immune reaction
  • Type IV: cell-mediated delayed hypersensitivity reaction that is delayed

The three first types are considered to be immediate hypersensitivity reactions since they happen after 24 hours. The fourth kind is known as delayed hypersensitivity reactions because it typically occurs for longer than 12 hours after being exposed to an allergen with the maximum time of reaction of between 72 and 48 hours.

Alternative Name

Type I Type II Type III Type IV
Hypersensitivity to allergens Hypersensitivity to cytotoxic chemicals Complex hypersensitivity to immune system Hypersensitivity caused by cells/ delayed kind of hypersensitivity


Type I Type II Type III Type IV
Antibody-mediated degranulation and granulocyte degranulation leading to the death of cells. The destruction by antibodies of cells that are healthy. Complex-mediated destruction of cells by antigens. T lymphocytes are responsible for elimination of the cells.

Primary Mediator

Type I Type II Type III Type IV
IgE IgG/IgM IgG/IgM Certain subsets of helper CD4+ T cells or T cells that are CD8+.

Other components that act as mediators

Type I Type II Type III Type IV
Mast cell, Basophils and histamine, among other drugs Complement, Neutrophils Complement, phagocytes, and K cells The macrophages, dendritic cells and Cykines

Time to react

Type I Type II Type III Type IV
In a matter of hours 8 to 5-8 hours 2-8 hours After 24 hours, but generally between 48 and 72 hours after contact.


Type I Type II Type III Type IV
Free to circulate (Soluble) Fixed on cells Free to circulate ( Soluble) Cell-bound or soluble

Antigen origin

Type I Type II Type III Type IV
Exogenous Exogenous or endogenous Endogenous or exogenous Endogenous or exogenous


Type I Type II Type III Type IV
Retained on the mast cell and in basophils. Free circulation Free to circulate Non-applicable


Type I Type II Type III Type IV
Allergen-specific IgE antibodies attach to mast cells through the Fc receptor. When the allergen of interest is bound to the IgE and cross-links with IgE results in the disgranulation in mast cells. IgG and IgM antibody can bind to a cell-specific antigen which triggers complement activation and cell destruction. IgG can also play a role in ADCC by macrophages, natural killer cells and neutrophils. Antigen-antibody complexes accumulate in tissues. Complement activation releases inflammation mediators and also recruits neutrophils. Inflammatory enzymes released by neutrophils harm tissues. Th2 cells release cytokines that activate macrophages as well as T cells that are cytotoxic.

Compliment activation

Type I Type II Type III Type IV
No Yes Yes No


Type I Type II Type III Type IV
Weal & flare Lysis and necrosis Erythema and the edema Erythema and induration

Transfer using serum

Type I Type II Type III Type IV
Serum can be used to transfer blood. Transfer of funds via passive Transfer via passive It is not possible to transfer via serum, but it is it is possible to transfer T cells


Type I Type II Type III Type IV
Quick, but not long-lasting Simple, but only for a short time Simple, but only for a short time Long-lasting, but difficult to master.


Type I Type II Type III Type IV
Asthma, Rhinitis, Atopic Eczema, Bee Sting Reaction Rhesus Incompatibility (Rh hemolytic disorder) Transfusion Reactions Autoantigens cause cell destruction Induced by drugs, Hemolytic Anemia Glomerulonephritis Systemic Lupus Erythematosus Farmer’s Lung Arthritis, Vasculitis The tuberculin reaction, the Granuloma development, Allergic contact skin rashes Type-1 diabetes

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