Localization of mammary tumor virus inside red blood cells of mice.

showed B particles on their surfaces in electron micrographs. On the basis of these and other studies, the authors suggested that B particles may be the only infectious form of MTV, occurring in both blood and mammary tissues. The present investigation was undertaken to determine whether MTV activity is inside or on the surface of the red blood cells and to test whether adsorption of B particles to the RBC surface could account for R-MTV activity of RBC's.