ABSTRACT
Immunotherapy is highly effective in appropriately selected patients with allergic disease. Whereas conventional vaccination strategies are employed to initiate and then boost Immunologic memory, allergen immunotherapy aims to subdue established immune responses mediated by IgE and allergen-specific memory T cells through controlled exposure to the offending allergen. Since subcutaneous injection [subcutaneous allergen immunotherapy (SCIT)] of sufficient native allergen to invoke immunoregulatory mechanisms can trigger unwanted IgE-mediated reactions, the amounts of allergen contained in injections are increased incrementally from low levels until a safe but sufficient maintenance dose can be achieved. Patient selection is important and the risk/benefit ratio must be assessed on an individual basis. The underlying mechanisms are important since they provide insight into the mechanisms of allergic disease and induction of clinical tolerance. In addition, allergen injection immunotherapy is allergen-specific. This enables one to observe the effects of specific modulation of the immune response in a patient in whom the provoking factor(s) (common aeroallergen or venom) are known. The effects of the allergen exposure may be observed either during experimental provocation in a clinical laboratory or during natural environmental conditions. Similarly, the influence of immunotherapy on clinical, Immunologic, and pathologic changes may be observed under controlled conditions. This is in contrast to other Immunologic diseases where the antigen is unknown and no antigen-specific treatment is available. Sublingual allergen immunotherapy (SLIT) is emerging as a viable clinical alternative to the traditional subcutaneous route, although there are very few published, wellcontrolled mechanistic studies (Chap. 2). This chapter will therefore focus entirely on mechanisms of injection immunotherapy, reflecting a collective research effort spanning several decades.
