The sublingual route of administration allows a direct contact of the antigens with the mucosal immunocytes of the mouth and the pharynx, inducing a loco-regional activation of the immune system. It also offers better immune surveillance along the mucosal barrier, since circulating memory cells preferentially return to the area of first encounter with the antigen.
It has been demonstrated that the sublingual mucosa contains a high number of dendritic cells, which explain the high T cell answer observed after treatment. And finally, the sublingual route allows increasing the level of salivary IgA which acts as a first line of defense in preventing respiratory infections.