[Antitumor resistance induced by immunization with normal definitive tissues]

Immunization of C3HA mice with homogenates of various normal definitive tissues, obtained from syngeneic, allogeneic and xenogeneic donors, resulted in an increase of antitumor resistance, as evidenced by a considerable retardation of growth of the transplantable strain-specific hepatoma 22a. The effect may be due to sensibilization of animals to the antigens of normal definitive cells, and, in particular to the tissue-specific antigens characteristic of cells of the tumor in question.