Morphogenesis of Two Immunologically Induced Mouse Lymphomas

Summary

Female BALB/c and DBA/2N mice were treated simultaneously with azathioprine and an antigen (LDH virus, tubercle bacteria, or bovine serum albumin). Experimental animals developed between 20 and 66% malignant lymphomas that were classified by light and electron microscopy as lymphoblastic types. The tumors developed in an atrophic thymus and subsequently spread to involve the remaining lymphoreticular and hemoreticular tissues, as well as nearly all other organs. Cytologically, the initial thymic tumor nodules did not differ from hyperplastic nodules of nonneoplastic lymphoblastic stem cells. Also, cells of a well-established tumor showed only slight differences from those of normal lymphoblastic stem cells, such as increased esterase activity and presence of cytoplasmic annulate lamellae. Virus particles (C-type) were identified by electron microscopy only in early tissue culture passages of the BALB/c lymphoma but not in the DBA lymphoma. All tumors were readily isotransplantable. Cell-free transplantation remained negative in all instances tried. The tumor grows in tissue culture as an established lymphoblast cell line.