The immune system uses specialized proteins called antibodies. Immunoglobulin E (IgE) is one such antibody, playing a specific role in allergic reactions. When the immune system overreacts to otherwise harmless substances, known as allergens, it produces IgE antibodies. Anti-IgE antibodies represent a targeted therapeutic approach designed to manage these overreactions by interfering with the function of IgE.
Understanding IgE and Allergic Responses
Immunoglobulin E (IgE) is a class of antibodies produced by the immune system. Normally, IgE antibodies contribute to the body’s defense against parasitic infections, such as worms. IgE antibodies recognize specific markers on parasites, triggering an immune response.
However, in individuals with allergies, the immune system mistakenly identifies harmless substances like pollen, dust mites, or certain foods as threats. Upon exposure to these allergens, the body produces large amounts of IgE antibodies. These IgE antibodies then attach to specialized immune cells called mast cells and basophils. When the sensitized mast cells and basophils encounter the specific allergen again, they release a variety of inflammatory chemicals, including histamine. This release of mediators leads to the familiar symptoms of an allergic reaction, such as itching, swelling, nasal congestion, and respiratory distress.
How Anti-IgE Antibodies Function
Anti-IgE antibodies work by specifically targeting and neutralizing IgE antibodies. These therapeutic antibodies are designed to bind to free IgE, preventing it from attaching to the high-affinity IgE receptors located on the surface of mast cells and basophils. This binding action makes IgE unavailable to participate in the allergic cascade.
By reducing the amount of free IgE that can bind to mast cells and basophils, anti-IgE therapy dampens the subsequent release of inflammatory mediators like histamine upon allergen exposure. This targeted approach helps to prevent or significantly reduce the severity of allergic symptoms.
Conditions Treated with Anti-IgE Therapy
Anti-IgE antibody therapy is approved and commonly used for several allergic conditions where IgE plays a central role. Omalizumab, marketed as Xolair, is a prominent example of an anti-IgE medication. It is approved for the treatment of moderate-to-severe persistent allergic asthma in individuals who are not adequately controlled by standard treatments like inhaled corticosteroids. In allergic asthma, omalizumab helps reduce the frequency and severity of asthma attacks, improves lung function, and can decrease the need for oral corticosteroids.
The therapy is also indicated for chronic spontaneous urticaria (CSU), a condition characterized by persistent hives with no identifiable cause. For patients with CSU who do not respond well to antihistamines, omalizumab can significantly reduce itch severity and the number of hives. Additionally, omalizumab is approved for chronic rhinosinusitis with nasal polyps, a condition involving inflammation of the nasal passages and sinuses with growths. In some regions, it is also indicated for IgE-mediated food allergy.
Practical Aspects of Anti-IgE Treatment
Anti-IgE treatment, such as omalizumab, is administered through subcutaneous injections. The frequency of these injections ranges from every two to four weeks, depending on the specific condition being treated and individual patient factors. The dosage and frequency for allergic asthma, food allergies, and nasal polyps are determined based on a patient’s body weight and their total serum IgE levels measured before treatment begins. For chronic spontaneous urticaria, injections are given every four weeks.
This therapy is considered for individuals whose conditions are not well-controlled by conventional treatments. For example, in allergic asthma, it’s used when patients have not responded to high-dose inhaled corticosteroids. Common side effects observed with anti-IgE therapy include reactions at the injection site, such as pain or swelling, headache, dizziness, tiredness, itching, and skin rash. While rare, severe allergic reactions, including anaphylaxis, can occur, sometimes even after several doses or with a delayed onset, necessitating careful monitoring by a healthcare professional.