The immunological status of allografts in the middle ear

In a series of experiments using two inbred rat strains differing in respect of their major histocompatibility antigens, and a sensitive test for antibody directed against major histocompatibility antigens, it was shown that (i) grafts known to be highly immunogenic (10(7)) lymphocytes) regularly immunized their hosts when injected intratympanically; the immune response could not be ascribed to leakage of cells into either the external auditory meatus or the nasopharynx, (ii) immunization occurred at least partly via the regional lymphatics, (iii) single orthotopic or heterotopic incus grafts immunized their hosts sporadically, and (iv) the variable immunization which followed single ossicular grafts was due to their relatively low content of antigen.