The properties of sarcomas induced in wistar rats by rous sarcoma virus (schmidt‐ruppin)

The properties of single cell clones derived from sarcomas induced in young Wistar rats by RSV (S‐R) are compared. Most sarcomas do not produce infectious RSV but are virogenic (i.e. capable of inducing Rous tumours) for chicks. One sarcoma was not virogenic. Clones were tested for virus release either alone in vitro or after passage on the chorioallantoic membrane of the embryonated egg. The avian sarcoma‐leukosis group‐specific (complement‐fixing) antigen could not be detected in either virogenic or non‐virogenic cells. A few primary Rous rat sarcomas showed the presence of virus‐induced transplantation antigen but this could not be detected by graft‐rejection in serially‐passed tumours, or in any of the clones. The virogenic clones were more malignant for rats than the non‐virogenic ones, but this property was not associated with the presence or absence of virus‐specific antigens.