Accelerated plasmacytoma formation in mice treated with alpha-fetoprotein.

The ability of alpha-fetoprotein (AFP), derived from mouse amniotic fluid, to alter qualitative and quantitative characteristics of pristane-induced plasmacytomas and the carcinogenic action of 3-methylcholanthrene (MCA) and 7,12-dimethylbenz]a[-anthracene (DMBA) was studied and compared to analogous treatment with murine albumin and transferrin in BALB/c mice. Pharmacologic doses of 200 microgram AFP ip three times per week had no effect on either latency period or tumor incidence in mice given injections of MCA and DMBA when compared to albumin-treated and transferrin-treated controls. Moreover, this lack of influence of AFP was found at high and low dosages of the carcinogens. In contrast AFP, but neither albumin nor transferrin, accelerated the appearance of plasmacytomas in pristane-primed BALB/c mice. Moreover, the immunoglobulin class of plasmacytomas of mice given AFP injections was qualitatively altered, and in increase in IgM and IgG2b plasmacytomas was noted. These effects occurred at serum AFP levels of 90--260 microgram/ml. Although these results should not be used to support a normal physiologic role of AFP in immune regulation, they are similar to previous observations of suppression mediated by the alpha-globulin fraction of normal serum and suggest that pharmacologic dosages of AFP may be useful in the study of select, possibly thymus-dependent, immune responses.