Immunopathology of NZB/BL mice. V. Viruslike (filtrable) agent separable from lymphoma cells and identifiable by electron microscopy.

A filtrable agent separable from transplantable malignant lymphomas of NZB/Bl mice was capable, upon inoculation into preweanling NZB/Bl mice, of inducing lymphoid cell hyperplasia, hypergammaglobulinemia, proteinuria, hypoalbuminemia, and pathological changes (focal membranous glomerulonephritis) of kidneys-renal functional and structural changes qualitatively similar to those of spontaneous occurrence in older NZB/Bl mice. Viruslike particles with close resemblance to the typical "C" type murine oncogenic virus particles were identified by means of electron microscopy in NZB/Bl mouse tissues and cells, including malignant lymphoma cells, benign lymphoid cells of thymus and spleen, epithelial cells of renal tubules, and extracellular sites. The relevance of these observations, the first of their kind dealing with NZB/Bl mice, is discussed in relation to the several immunopathological disorders which characterize this strain of mice.