The key difference between immediate and delayed hypersensitivity is that immediate hypersensitivity is a type of allergic reaction that occurs within 24 hours, while delayed hypersensitivity is a type of allergic reaction that occurs within 48 to 72 hours.
Hypersensitivity reactions are exaggerated immunologic responses that occur in response to an antigen or allergen. They are classified as type I, II, III, and IV. Type I, II, and III hypersensitivity reactions are called immediate hypersensitivity reactions because they occur within 24 hours of exposure to the antigens or allergens, while type IV hypersensitivity reaction is called delayed hypersensitivity reaction since it occurs after 24 hours.
CONTENTS
1. Overview and Key Difference
2. What is Immediate Hypersensitivity
3. What is Delayed Hypersensitivity
4. Similarities – Immediate and Delayed Hypersensitivity
5. Immediate vs. Delayed Hypersensitivity in Tabular Form
6. Summary – Immediate vs Delayed Hypersensitivity
What is Immediate Hypersensitivity?
According to Coombs and Gell classification, hypersensitivity reactions are categorized into four forms. Type I, type II, and type III hypersensitivity reactions are known as immediate hypersensitivity reactions or immediate hypersensitivity. These reactions occur within 24 hours. The antibodies mediating the immediate hypersensitivity are IgE, IgM, and IgG.
Type I hypersensitivity reaction is also called anaphylactic response. They are mediated by IgE antibodies produced by the immune system in response to allergens such as pollens, animal danders, or dust mites. Type II hypersensitivity reaction is an antibody-mediated response in which IgG and IgM work against cell surface and extracellular matrix proteins. Type II hypersensitivity reactions can usually be seen in immune thrombocytopenia, autoimmune hemolytic anemia, and autoimmune neutropenia. Furthermore, type III hypersensitivity reactions are also mediated against soluble antigens. This type of reaction is classically seen in serum sickness and Arthus reaction.
Immediate hypersensitivity can be evaluated by complete blood cell counts, assessment of immunoglobulins, skin prick tests, or the detection of autoantibodies. The treatment for immediate hypersensitivity includes epinephrine, oxygen therapy, IV antihistamines, blood pressure support with IV fluids, avoiding certain products such as latex gloves and equipment, inhaling short or long-acting bronchodilators along with inhaled corticosteroids, leukotriene antagonist, use of disodium cromoglycate, environmental controls, nonsteroidal anti-inflammatory drugs and hydroxychloroquine and monoclonal antibodies such as omalizumab.
What is Delayed Hypersensitivity?
According to Coombs and Gell classification, type IV hypersensitivity reaction is known as delayed hypersensitivity reaction or delayed hypersensitivity. A delayed hypersensitivity reaction occurs within 48 to 72 hours after exposure to allergens. Antibodies are not involved in this type of hypersensitivity. Instead, the antigen activates eosinophils, monocytes, or lymphocytes called T cells and is involved in the hypersensitivity reaction. In this type of hypersensitivity, initially, CD4+ T cells recognize the antigen. Then they release cytokines that activate the killer CD8+ T cells (to destroy the target cells on contact) and macrophages (to wall off the antigen and to prevent further damage). Type IV hypersensitivity reaction can usually be seen in allergic contact dermatitis (to hair dye, nickel in jewelry, Toxicodendron spp.), delayed drug reaction (morbilliform drug reactions, lichenoid drug eruptions, erythema multiforme, and Steven-Johnson syndrome (SJS)).
Delayed hypersensitivity can be evaluated by medical history, physical examination, and patch testing. Furthermore, treatment options for delayed hypersensitivity may include avoidance of contact, emollients and topical steroids, systemic corticosteroids, and monoclonal antibodies (omalizumab, rituximab, and anti-complement monoclonal antibody).
What are the Similarities Between Immediate and Delayed Hypersensitivity?
- Immediate and delayed hypersensitivity are two different types of hypersensitivity reactions.
- Antigens or allergens trigger both.
- They can be evacuated through physical examination and skin prick testing.
- They are treated through corticosteroids and monoclonal antibodies.
What is the Difference Between Immediate and Delayed Hypersensitivity?
Immediate hypersensitivity is a type of allergic reaction that occurs within 24 hours, while delayed hypersensitivity is a type of allergic reaction that occurs within 48 to 72 hours. Thus, this is the key difference between immediate and delayed hypersensitivity. Furthermore, immediate hypersensitivity is an allergic reaction that IgE, IgM, and IgG mediate, while delayed hypersensitivity is a type of allergic reaction mediated by CD8+ cells and macrophages.
The infographic below presents the differences between immediate and delayed hypersensitivity in tabular form for side-by-side comparison.
Summary – Immediate vs. Delayed Hypersensitivity
Hypersensitivity is an abnormal or exaggerated physiological reaction in which there is an adverse immune response to antigens. There are four forms: type I, type II, type III, and type IV hypersensitivity reactions. Type I, type II, and type III hypersensitivity reactions are known as immediate hypersensitivity, while type IV hypersensitivity reaction is known as delayed hypersensitivity. Furthermore, immediate hypersensitivity occurs within 24 hours, while delayed hypersensitivity occurs within 48 to 72 hours. So, this summarizes the difference between immediate and delayed hypersensitivity.
Reference:
1. “Immediate Type Hypersensitivity.” An Overview | ScienceDirect Topics.
2. “Type IV Hypersensitivity Reaction.” – Statpearls – NCBI Bookshelf.
Image Courtesy:
1. “2228 Immune Hypersensitivity new” By OpenStax College – Anatomy & Physiology, Connexions Web site, Jun 19, 2013. (CC BY 3.0) via Commons Wikimedia
2. “Blausen 0014 Allergic Dermatitis” By Blausen.com staff (2014). “Medical Gallery of Blausen Medical 2014”. WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.010. ISSN 2002-4436. – Own work (CC BY 3.0) via Commons Wikimedia