Abstract: A unique gene sequence encoding a suppressin protein has been isolated. Using recombinant DNA techniques, the suppressin protein may be produced in useful quantities. Methods for preparing the gene sequence and the gene product are disclosed. Also provided are novel plasmids and host cells.

Abstract: Mammalian pituitary discovered anti-proliferation factor that inhibits in vitro cellular proliferation of lymphoid, neuroendocrine and neural cells but not of fibroblast or endothelial cells. The present invention is directed to this antiproliferation factor which has been named suppressin and is a protein of Mr 63,000, sensitive to reduction and has a pI of 8.1. Suppressin is provided as a cell free preparation or in homogeneous form. The invention provides methods to purify suppressin, antibodies against suppressin and their use recombinant DNA molecules encoding suppressin, and pharmaceutical compositions for inducing regression or inhibiting growth of tumor or cancel cells and autoimmune diseases.