Immune functions in methyl and ethyl carbamate treated mice.

Female B6C3F1 hybrid mice (5-7 weeks of age) were given methyl or ethyl carbamate over a 2 week period and subsequently examined for alterations in various immunological parameters. Exposure to methyl carbamate, a non-carcinogen, did not cause any alterations in the parameters examined. In contrast, exposure to the multipotential carcinogen, ethyl carbamate (urethan) at tumourigenic dosages caused severe myelotoxicity at all dosage levels. Related to the myelotoxicity was a marked depression of natural killer cell activity. Other parameters including susceptibility to tumour cell challenge, humoral immunity, cellular immunity and macrophage function were less affected. These studies indicate that non-toxic, but carcinogenic dosages of urethan, have profound but selective effects on the immune system which can be related to alterations in bone marrow functions.