Basic science for the clinician: Mechanisms of sublingual and subcutaneous immunotherapy

To discuss the general immunologic changes that occur during immunotherapy, focusing on the differences between subcutaneous immunotherapy (SCIT) and sublingual immunotherapy (SLIT).

PubMed literature review.

Articles pertaining to SCIT and SLIT, with specific emphasis on those that included immune mechanistic studies.

Both SCIT and SLIT are characterized by the induction of regulatory B and T cells, decreased allergen-specific T-cell proliferation, a shift from a TH2 to TH1 cytokine milieu and from an IgE to an IgG4/IgA antibody response. These changes are accompanied by clinical improvement in symptoms.

Immunotherapy using allergen extracts administered via both subcutaneous and sublingual approaches have demonstrated efficacy in the treatment of allergic rhinoconjunctivitis and other allergic conditions. There are subtle differences between the approaches, and understanding these differences may help clinicians select a preferred route of therapy for particular patients or allergens, depending on the immune response that is being targeted.