Type C retrovirus activation and possible functions in the normal and tumor-bearing host

The pathological consequences of tumor virus infection, transformation, and tumor development in certain experimental animals is a well-established and accepted fact. More recently, it has been suggested that these viruses may also have a physiological function participating in such processes as cellular differentiation, immune recognition, and embryogenesis. This paper delineates the current information giving some credence to physiological function for type C viruses.