[Control of the mutagenicity of a new immunomodulator]

New immunostimulator STP, peptide isolated from the cultivation medium of Streptococcus species producer strain TOM-1606 by chromatographic purification, was controlled for mutagenicity. The preparation, introduced into mice in doses of 6.7 X 10(2) - 6.7 X 10(4) micrograms/kg, i.e. exceeding the stimulating dose 1000-fold, did not induce the appearance of micronuclei in polychromatophilic erythrocytes of the marrow, the fixation of the material being made 24, 48 and 72 hours after the injection. In Ames' test on Salmonella typhimurium strains TA 98 and TA 100 neither native STP, nor STP activated with the microsomal fraction of rat liver enzymes did not increase the frequency of reversions to histidine independence. The absence of mutagenic properties in STP was demonstrated by the parallel pronounced genotoxic action of a number of known mutagens used as positive controls.