Allergic Encephalitis and Its Possible Relationship to Human Disease

Abstract

Allergic encephalitis is an inflammatory and degenerative process in the brain of animals produced by the parenteral injn. of homologous or heterologous brain tissue. It is characterized clinically by ascending paralysis and high mortality, and pathologically by venous dilatation, perivascular infiltration and intense circum-venous microglial proliferation and leukocytic infiltration with partial demyelination of included white matter. Both clinically and pathologically the exptl. disease bears considerable resemblance to human post-vaccinal encephalitis, but is much more acute than mulitple disseminated sclerosis and lacks the characteristic late scarred stages. Incorporation of the brain tissue for injn. in the Freund adjuvant[long dash]water-in-oil emulsion with acid-fast bacilli[long dash]greatly increases the speed and regularity with which the encephalitis can be produced. The role played by the ingredients of the Freund adjuvant, and the reaction of various types of brain tissue and brain extractives are discussed. It appears that the encephalitogenic factor is somehow connected with the phosphatide fraction of brain tissue. It is water-soluble, can be removed from rabies vaccine by treatment with Ca acetate, and is dialysable through a cellophane membrane.