Abstract
A soluble fraction containing transplantation antigens was isolated from cells infected with adenoviruses and from the membrane fraction from cells of adenovirus-induced hamster tumours. It was not identified either as a part of the virus structure or as a T antigen. This material regularly protected young adult hamsters against the development of tumours resulting from the transplantation of adenovirus tumour cells. Protection was given by soluble antigens isolated from more than one cell type; the antigens could be induced by at least two groups of adenovirus, with probable cross-protection within groups. The antigens did not protect animals challenged with tumour cells produced by a different DNA virus, SV40.