ABSTRACT
Infection of susceptible hosts with oncogenic RNA viruses invariably leads to an alteration of immunological functions. Thus far, the observation holds true for all animal species and viruses examined. Justification for research in this area is based on several lines of rationale. The chapter focuses on primary mechanisms whereby immunosuppression appears to be an early consequence of virus infection, preceding the overt disease. The immunodeficiency accompanying oncornavirus-induced sarcomas, lymphomas and leukemias could be related to the infection itself i.e., early, primary immunosuppression or to the secondary effects of the progressive malignancy on the immune system. The chapter considers evidence supporting the direct mechanism of immunosuppression whereby the function of an immunocompetent cell is shut off because of infection by the virus. The immunosuppression of the cell may be related to any of the distinct viral functions, or it may be viewed as yet another independent function of the virus.
