Immunotherapy

Andrew G. Ayars, MD, and Matthew C. Altman, MD, MPhil

Introduction/Etiology/Epidemiology

•An “allergy” is an immune-mediated hypersensitivity response to an otherwise benign substance, such as aeroallergens, medications, venoms, or foods.

•Both allergic rhinitis and allergic asthma represent some of the most common chronic childhood illnesses in developed countries.

•These conditions cause clinically significant morbidity, including loss of productivity in the workplace or at school and increased treatment-related costs.

•Desensitization is a process by which a diminished responsiveness to an allergen is achieved via repeated administration of an allergen to which a patient is sensitized.

•Immunotherapy is currently the only available therapy that can result in a desensitization to aeroallergens.

—The treatment is available as subcutaneous or sublingual immunotherapy.

—Immunotherapy has been shown to be effective in both allergic rhinitis and allergic asthma.

•Venom immunotherapy will not be discussed in this chapter.

•Oral immunotherapy for food allergies is being increasingly studied but will not be discussed in this chapter.

Mechanism of Action

•Immunotherapy alters the underlying immune response to aeroallergens.

•Prolonged administration of immunotherapy has been associated with the following:

—Induction of regulatory T cells, resulting in suppression of the proinflammatory T helper (T_h2 and T_h1) cells

—Decreased allergen-specific lymphocyte proliferation

—Decreased specific immunoglobulin E (IgE) and increased specific immunoglobulin G4 response to aeroallergens

Indications

•Allergic rhinitis: Characterized by periodic rhinorrhea, postnasal drip, congestion, and sneezing; often associated with allergic conjunctivitis (itchy, watery eyes)

•Immunotherapy is often indicated in the following patients:

—Patients with symptoms that are uncontrolled despite medical therapy and environmental controls

—Those who do not tolerate medications or who would like to try to decrease medication use

—Those with a documented IgE-mediated hypersensitivity that correlates with the clinical history

•Prescribing immunotherapy

—Clinicians prescribing immunotherapy should have knowledge of

▪The local aeroallergens prevalent in the area

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