Early morphological Changes Associated With Infection by a Murine Nonthymic Lymphatic Tumor Virus

Summary

The early pathologic picture of solid lymphatic tumors induced in mice with a virus (MLV-A) was studied in BALB/cCr mice. (The abbreviation MLV-A is used as a tentative designation for the Abelson isolate, pending ultimate determination of its relationship with Moloney leukemia virus.) Animals were inoculated with MLV-A on the 1st day of life and were randomly killed at daily intervals from days 4–26. The histology of the virus-inoculated animals was compared with that of control mice, with special attention being directed to lymphoid and hematopoietic organs. Tissues from tumor-bearing animals were examined with the electron microscope. After day 15, the spleens of virus-inoculated animals were consistently enlarged and hyperplastic, but no tumor was present. After a short latent period, tumors appeared in lymph nodes, bone marrow, and the meninges. They grew rapidly and invaded the surrounding tissues. The blood was not leukemic, and visceral organs were not infiltrated. The thymus appeared normal during the premalignant period and was never involved with tumor. The tumor cells appeared to be predominantly lymphoblasts. Budding type-C particles were present in tumor tissue and also in non-tumorous tissue (spleen, bone marrow, thymus, and dura). The pathologic picture produced by MLV-A is significantly different from that produced by the well-characterized murine leukemia viruses.