Types of Hypersensitivity
Hypersensitivity, which is also called hypersensitivity reaction or intolerance, refers to undesirable reactions produced by the normal immune system, including allergies and autoimmunity. People with allergies, no matter what kind, have varying degrees or levels of severity. The response of the host to the presence of foreign substances can trigger four types of reactions. The traditional classification for hypersensitivity reactions is that of Gell and Coombs, and is considered the most common classification system.
Type I hypersensitivity or immediate hypersensitivity
This type of reaction is an allergic reaction caused by re-exposure to an allergen. It involves immunoglobulin E (IgE)-mediated release of histamine and other mediators from mast cells and basophils.
Some examples include allergic asthma, allergic conjunctivitis, allergic rhinitis or hay fever, anaphylaxis, angioedema, urticaria, eosinophilia, penicillin allergy, cephalosporin allergy, food allergy, and sweet itch.
Type II hypersensitivity reactions (ie, immediate hypersensitivity reactions)
Type II hypersensitivity reaction involves antibody mediated destruction of cells, also known as cytotoxic reaction. In this type, specific antibody (IgG or IgM) bound to cell surface antigen and destroy the cell.
Examples:
- Acute hemolytic transfusion reaction
- Autoimmune hemolytic anemia
- Bullous pemphigoid
- Pemphigus vulgaris
- Rheumatic fever
- Drug-induced neutropenia and agranulocytosis
- Goodpasture syndrome
- Graves disease
- Hemolytic disease of the fetus and newborn
- Immune thrombocytopenia (ITP)
- Hyperacute transplant rejection
- Myasthenia gravis
- Pernicious anemia
Type III hypersensitivity reactions
Type III hypersensitivity reactions are also called immune complex reactions. Type III Hypersensitivity is tissue damage created by immune complexes. Immune Complexes are aggregations of antigen and antibodies. When the amount of antigen and antibody is comparable, immune complexes can form.
Examples:
- Arthus reaction
- Drug-induced hypersensitivity vasculitis
- Hypersensitivity pneumonitis
- Polyarteritis nodosa (PAN)
- Poststreptococcal glomerulonephritis, IgA nephropathy, membranous glomerulopathy, lupus nephritis
- Serum sickness
- Serum sickness-like reaction (atypical without circulating immune-complex involvement)
- Systemic lupus erythematosus (SLE)
Type IV hypersensitivity reactions
Type IV Hypersensitivity is also called delayed hypersensitivity and involves Th1 T-Cells attracting and activating Macrophages. It is called delayed because it takes a few days to kick in. This type is Cell-Mediated and Antibody Independent. Type IV Hypersensitivity is the only type of hypersensitivity that doesn’t involve antibodies.
Examples:
- Acute and chronic transplant rejection
- Contact dermatitis (e.g., nickel, poison ivy, cosmetics, rubber gloves)
- Drug reactions (e.g., Stevens-Johnson syndrome, toxic epidermal necrolysis, drug reaction with eosinophilia and systemic symptoms (DRESS)
- Graft-versus-host disease
- Mantoux tuberculin skin test for latent tuberculosis
- Candida skin test
- Multiple sclerosis
- Guillain-Barré syndrome
- Hashimoto's thyroiditis
- Rheumatoid arthritis
- Type 1 diabetes mellitus
In latex allergy, there are three types of reactions to natural rubber latex: IgE-mediated allergic reactions (Type I), or true allergic reactions involving the immune system and can be life-threatening, cell-mediated contact dermatitis (Type IV), and irritant dermatitis.
In type I, IgE reacts with natural rubber proteins, causing a reaction. It can be through direct skin contact, contact with a mucous membrane such as the mouth, or inhalation. Meanwhile, type IV is usually due to sensitivity to chemicals used to make latex products, rather than to rubber proteins. When these chemicals come into contact with skin, it can cause contact dermatitis 24 to 48 hours after exposure. This type of dermatitis can spread to other areas, but the symptoms usually resolve spontaneously. Irritant dermatitis on the other hand, is a common reaction to natural rubber latex, but is not an allergy. Symptoms such as rashes break out where latex has touched the skin, but usually subside 12 to 24 hours after contact.
Four out of five people who develop IgE-mediated latex allergy will have contact dermatitis first. If you have this, work with your doctor to learn how to recognize anaphylaxis and how to treat it.
Sources: