IMMUNOSUPPRESSIVE ACTIVITY OF ANGIOGENIN IN COMPARISON WITH BOVINE SEMINAL RIBONUCLEASE AND PANCREATIC RIBONUCLEASE

Angiogenin, a member of the pancreatic-like ribonuclease family with a special biological action (RISBAses), is a basic protein that induces blood vessel formation. Another member of these special ribonucleases , bovine seminal ribonuclease (BS RNase), displays biological properti es, including aspermatogenic, embryotoxic, antitumor and immunosuppres sive activities. The effects of two angiogenin preparations tested on the biological activities mentioned above are reported and compared wi th those of BS RNase and RNase A. In contrast to RNase A, which was in effective in all biological activities tested, angiogenin suppressed s ignificantly the proliferation of human lymphocytes stimulated by phyt ohemagglutinin or concanavalin A or by allogenic human lymphocytes (mi xed lymphocyte culture). However, angiogenin did not affect the growth of human tumor cell lines, development of cow acid mouse embryos and spermatogenicity in mice. On the basis of these results, angiogenin is the first monomeric ribonuclease described so far that displays immun osuppressive activity similar to that of the dimeric BS RNase. The imm unosuppressive activity of angiogenin might synergize with the effect on neovascularization of tumor tissues and thus contribute to the deve lopment of tumor.