"Nucleolar test" as a system for screening and analysis of immunosuppressive activity of chemical and biological agents.

The numbers and nucleolar activity of lymphocytes were followed in the control and SRBC-stimulated popliteal lymph nodes following administration of known immunosuppressive agents of different classes which were given in doses effective in the Jerne test and graft-versus-host reaction. Immunosuppressive agents had a non-selective effect on different lymphocyte populations (characterized by the activity of nucleolar RNA synthesis) in the control, antigen-untreated lymph nodes, but had a marked inhibitory effect on lymphocytes with compact nucleoli in the antigen-stimulated lymph nodes. This decrease is in good correlation with suppression of the Jerne haemolytic plaques and GVHR. The nucleolar test as a simple technique appears to be adequate for a rapid screening of immunosuppressive activity of the chemical and biological agents.