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Containing dedicated Learning Zones, guidelines, trials and news for related conditions in Immunology
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Allergy and immunology

Containing dedicated Learning Zones, guidelines, trials and news for related conditions in Immunology
Last updated: 5th Mar 2024

What are the components of the immune system?

The immune system is made up of the innate immune system and adaptive immune system. The innate immune system is the first-line, non-specific response to pathogens, such as bacteria and viruses. In the innate immune response, inflammatory cells, such as phagocytes and natural killer cells, destroy the pathogen. The adaptive immune system produces a slower response that targets the pathogen specifically using antibodies and cells like T lymphocytes and B lymphocytes. There are many different types of immune system disorders that can affect all the major body systems, including hypersensitivities and allergies, immune deficiencies and autoimmune diseases1.

What is immune hypersensitivity?

Hypersensitivities and allergies are responses that occur when the body responds inappropriately to antigens that are usually non-pathogenic, called allergens. Local atopic responses include asthma, contact dermatitis, urticaria and rhinitis. Other types of hypersensitivities include drug allergies and food allergies. A food allergy can occur in response to any of the 14 major allergens, including peanuts, milk and eggs. Severe food allergies can lead to anaphylaxis, a life-threatening condition. Immune cells involved in these hypersensitive immune responses are primarily leukocytes, such as T cells, monocytes, macrophages, eosinophils, basophils and mast cells2,3.

What are immunosuppressive disorders?

Immunosuppression, or immunodeficiency, is temporary or permanent weakening or suppression of the immune system. Immune suppression can arise from a variety of sources, including inherited or congenital diseases, also known as primary immunodeficiency disorder (PID), or primary immune deficiency diseases (PIDDs)4,5. Immunosuppression can also arise from acquired and/or chronic medical health conditions, such as heart disease, lung disease, diabetes, cancer and human immunodeficiency virus (HIV)6. Finally, immunosuppression can be caused by certain treatments such as chemotherapy, pregnancy, and short-lived infections like influenza. Immunocompromised patients are more likely to pick up opportunistic infections, like Covid-19, than people who are not immunocompromised7.

What are autoimmune disorders?

Autoimmune diseases, or autoimmunity, occur when adaptive immune cells that recognise host cells are unchecked, so the immune system attacks healthy host cells. Autoimmune diseases include psoriasis, psoriatic arthritis, rheumatoid arthritis, ulcerative colitis, crohn’s disease, systemic lupus erythematosus (lupus) and thyroid diseases. Autoimmune disorders are often associated with an inflammatory response which can cause acute inflammation or chronic inflammation8.

What is immunotherapy?

Immunotherapy is used to treat diseases by modulating the immune system, either by activation or suppression of the immune system. There has been much focus on immunotherapy for cancer treatment (cancer immunotherapy, or immuno-oncology) in recent years. Cancer immunotherapies include immune checkpoint inhibitors, T-cell transfer therapy, monoclonal antibodies (mAbs), treatment vaccines and immune system modulators9.

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  2. Valenta R, Hochwallner H, Linhart B, Pahr S. Food Allergies: The Basics. Gastroenterology. 2015;148:1120–1131.
  3. Mak TW, Saunders ME, Jett BD (2014). Immune Hypersensitivity. In: Primer to the Immune Response (Second Edition) [Internet]. Available at: (Accessed May 2021).
  4. National Institute of Allergy and Infectious Diseases, 2014. Available at: (Accessed May 2021).
  5. McCusker C, Upton J, Warrington R. Primary immunodeficiency. 2018;14 (Suppl 2):141–152
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  9. National Cancer Institute (2019). Available at: (Accessed May 2021).