Antigen resorption from the gastrointestinal tract: A historical perspective on the pathophysiological foundation of modern sublingual/oral immunotherapy

Resorption of small particles and proteins through the mucous membranes of the intestines has been extensively studied for well over a 100 years and the arrival of sublingual/ oral immunotherapy in clinical practice has renewed interest in this process. The first line of immune response to a potential allergen is at the site of contact with a mucous membrane and both inhaled and ingested allergens usually lead to some level of direct clinically appreciable manifestation on the mucous membrane. The initial process of antigen resorption has been relatively well understood for almost one century; however, the metabolic and/or immunological fate of large particles is the subject of more recent studies. We now recognize that resorption and hematogenous spread of biologically intact allergens from the gastrointestinal tract occur despite extensive predigestion of particles and proteins within the gastrointestinal lumen and this phenomenon provides the pathophysiological underpinning of modern sublingual/oral immunotherapy.