Archives of General Internal Medicine

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Opinion Article - Archives of General Internal Medicine (2024) Volume 8, Issue 3

The Immunological Basis of Allergic Reactions: From Sensitization to Symptoms

Bianang Li *

Department of Apicultural Research, Chinese Academy of Agricultural Sciences, China

*Corresponding Author:
Bianang Li
Department of Apicultural Research, Chinese Academy of Agricultural Sciences, China
E-mail: libiangng@caas.cn

Received: 31-May-2024, Manuscript No. AAAGIM-24-136836; Editor assigned: 03-Jun-2024, PreQC No. AAAGIM-24-136836 (PQ); Reviewed: 17-Jun-2024, QC No. AAAGIM-24-136836; Revised: 19-Jun-2024, Manuscript No. AAAGIM-24-136836 (R); Published: 26-Jun-2024, DOI:10.35841/aaagim-8.3.239

Citation: : Li B. The immunological basis of allergic reactions: From sensitization to symptoms. Arch Gen Intern Med. 2024;8(3):239.

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Introduction

Allergic reactions are hypersensitive immune responses to typically harmless substances known as allergens. These responses are mediated by the immune system and involve a series of complex biological processes. Understanding the immunological basis of allergic reactions, from sensitization to symptom manifestation, provides insights into their mechanisms and potential therapeutic approaches. Sensitization is the initial phase of an allergic reaction, occurring when the immune system first encounters an allergen. During this phase, the immune system mistakenly identifies the allergen as a harmful invader. The key steps in sensitization include: Allergens enter the body through inhalation, ingestion, or skin contact. Common allergens include pollen, dust mites, animal dander, certain foods, and insect venoms [1, 2].

The allergens are processed by Antigen-Presenting Cells (APCs), such as dendritic cells, which then present the allergen-derived peptides on their surface via Major Histocompatibility Complex (MHC) molecules to T cells. Allergen-specific CD4+ T helper cells (Th2 cells) become activated upon recognizing the allergen peptides presented by APCs. These Th2 cells secrete cytokines such as IL-4, IL-5, and IL-13, which are critical for orchestrating the allergic response. The cytokines produced by Th2 cells promote the activation and differentiation of B cells into plasma cells that produce allergen-specific Immunoglobulin E (IgE) antibodies. These IgE antibodies bind to high-affinity Fc receptors (FcεRI) on the surface of mast cells and basophils, sensitizing them to the allergen [3, 4].

Upon subsequent exposure to the same allergen, the body’s sensitized mast cells and basophils trigger an immediate hypersensitivity reaction. This effector phase involves: Allergen Binding and Cross-linking: When the allergen re-enters the body, it binds to the IgE antibodies on the surface of mast cells and basophils, causing cross-linking of the FcεRI receptors. Cross-linking triggers the degranulation of mast cells and basophils, leading to the release of pre-formed mediators such as histamine, tryptase, and heparin, as well as the synthesis of new mediators including leukotrienes, prostaglandins, and cytokines [5, 6].

Histamine, one of the key mediators, causes vasodilation and increases vascular permeability, leading to symptoms such as redness, swelling, and itchiness at the site of allergen exposure. The clinical symptoms of allergic reactions vary depending on the allergen and the route of exposure. Common manifestations include: Inhaled allergens, such as pollen or dust mites, can cause allergic rhinitis (hay fever) and asthma. Symptoms include nasal congestion, sneezing, itching, and wheezing [7, 8].

Understanding the immunological mechanisms underlying allergic reactions has paved the way for various therapeutic approaches: These drugs block histamine receptors, alleviating symptoms such as itching, sneezing, and hives. Anti-inflammatory medications that reduce inflammation and immune responses in allergic conditions. Allergen-specific Immunotherapy (AIT) involves the gradual introduction of increasing amounts of the allergen to build tolerance and reduce sensitivity. This approach aims to shift the immune response away from a Th2-dominated profile. Monoclonal antibodies targeting specific components of the allergic pathway, such as anti-IgE (omalizumab), have shown efficacy in treating severe allergic conditions by preventing IgE from binding to its receptors on mast cells and basophils [9, 10].

Conclusion

Allergic reactions are the result of complex immunological processes, starting from sensitization to the effector phase, culminating in various clinical symptoms. Advances in understanding the immunological basis of these reactions have led to improved diagnostic and therapeutic strategies, offering better management and quality of life for individuals with allergies. Ongoing research continues to unravel the intricacies of allergic responses, paving the way for novel treatments and potential preventive measures.

References

  1. Sicherer SH, Sampson HA. Food allergy: epidemiology, pathogenesis, diagnosis, and treatment. J Allergy Clin Immunol. 2014;133(2):291-307.

    2. Indexed at, Google Scholar, Cross Ref

  2. Fonacier L, Frankel D, Mawhirt S. Contact allergens for the allergist. Ann Allergy Asthma Immunol. 2022;128(6):629-44.

    3. Indexed at, Google Scholar, Cross Ref

  3. Parashar S, Pandya A, Portnoy JM. Pediatric subcutaneous allergen immunotherapy. Allergy Asthma Proc. 2022;43:4.

    4. Indexed at, Google Scholar, Cross Ref

  4. Herz U. Immunological basis and management of food allergy. J Pediatr Gastroenterol Nutr. 2008;47:S54-7.

    5. Indexed at, Google Scholar, Cross Ref

  5. Passalacqua G, Bagnasco D, Canonica GW. 30 years of sublingual immunotherapy. Allergy. 2020; 75(5):1107-20.

    6. Indexed at, Google Scholar, Cross Ref

  6. Kiewiet MG, Lupinek C, Vrtala S, et al. A molecular sensitization map of European children reveals exposome?and climate?dependent sensitization profiles. Allergy. 2023;78(7):2007-18.

    7. Indexed at, Google Scholar, Cross Ref

  7. Fuhrmann V, Huang HJ, Akarsu A, et al. From allergen molecules to molecular immunotherapy of nut allergy: a hard nut to crack. Front Immunol. 2021;12:742732.

    8. Indexed at, Google Scholar, Cross Ref

  8. Ferreira F, Hawranek T, Gruber P, et al. Allergic cross?reactivity: from gene to the clinic. Allergy. 2004;59(3):243-67.

    9. Indexed at, Google Scholar, Cross Ref

  9. Bostan OC, Cakmak ME, Kaya SB, et al. The association of timothy grass allergy and cat ownership on cat sensitization. Allergy Asthma Proc. 2022;43:3.

    10. Indexed at, Google Scholar, Cross Ref

  10. Cecchi L, Poncet P, Maltagliati L, et al. Optimization of the diagnosis and characterization of gibberellin-regulated protein sensitization: An Italian cohort study. Ann Allergy Asthma Immunol. 2024;132(1):82-90.

    11. Indexed at, Google Scholar, Cross Ref

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