Immunosuppressive properties of the antibiotics cytostipin and vermiculine.

The properties of two antibiotics, cytostipin isolated from Penicillium stipitatum and vermiculine isolated from Penicillium vermiculatum, were examined in two systems for a rapid screening of current immunosuppressive agents [nucleolar test determining the degree of RNA synthesis in nucleoli of individual lymphocyte populations, and the reactivity of mouse lymphocytes to "T" (PHA) and "B" (LPS) mitogens]. Both antibiotics, distinctly suppressed the increase in number of "active" lymphocytes with compact nucleoli in the popliteal lymph node activated by SRBC. Incorporation of 3H-uridine into PHA-stimulated "T" lymphocytes was suppressed by both antibiotics, incorporation into LPS-stimulated "B" lymphocytes was inhibited by cytostipin but stimulated by vermiculine. The antibiotics were also tested in another two "classic" immune systems, the Jerne test and the GVH reaction. Both antibiotics in doses markedly inhibitory for GVH reaction did not suppress but significantly increased the number of the haemolytic plaques in spleens of SRBC-immunized mice.