THE ROLE OF EPITHELIUM IN EXPERIMENTAL IMMUNIZATION

When a small amount of blood serum is dropped into the nose of a guinea pig the serum is absorbed by the mucous membrane and, after a definite period of incubation, the animal can be shown to have become profoundly changed. Depending upon the number of instillations, the interval between them and, especially, the quantity of serum instilled, the animal becomes either highly hypersensitive or strongly resistant to a toxic injection given by the vein. This resistance withstands a considerable series of increasing toxic injections and is strengthened with lapse of time,-contrary to the state of tolerance produced by traumatic methods. It is inferred that the absorption of foreign protein by the nose causes the formation of two different antibodies. One of these is allergic and excites to anaphylaxis; the other is protective and leads to true immuuity. The relative amount of either antibody can be regulated by modifying the amount of serum instilled. Added to a state of general allergy it is easy to produce, in the guinea pig, a special sensitization of the respiratory apparatus which leads, under appropriate stimulation, to attacks resembling those of bronchial asthma in man. No conclusion can be drawn at present concerning the nature or mode of action of the protective or immunizing antibody; but the indications are that its relations to the circulation and to tissue fixation resemble those which have been developed by other investigators in regard to the anaphylactic antibody. Evidence has been submitted that the living epithelium mediates between foreign protein and the organism in a way to favor specifically the elaboration of true immunity.