Electron microscopical study of rowson‐parr virus infection in balb/c mice

The significant electron microscopic changes in the course of Rowson‐Parr virus infection in BALB/c mice are described. In the early splenomegaly there is active folding of cell membranes of reticulum cells of the spleen in germinal centres and red pulp. Type‐C virus particles are seen between the folds, but not budding from these cells. This change is interpreted as the localization of virus antigen prior to specific antibody production. Plasma cells are present in considerable numbers in the red pulp soon after. These changes persist to a lesser degree in the spleen throughout the period when it is of normal size. The cells constituting the lymphoma resemble other murine lymphomas and are also characterized by the frequent appearance of type‐C virus particles budding from their surfaces. Electron microscopy of negatively stained centrifuged plasma was also carried out. In the first 4 days single scattered virus particles of typical murine oncogenic type are present, but these become agglutinated from the 5th day onwards. Perivascular mononuclear cell infiltrates are present in the kidneys after the 30th week. These are composed of plasma cells and reticulum cells with folded membranes, enclosing virus particles. The lymphoma in RPV infection thus develops at the site of and following a prolonged period of immunological reaction to the virus.