The effect of dimethylnitrosamine on host resistance and immunity.

Adult female B6C3F1 mice were injected ip with 0.2 ml phosphate-buffered saline (PBS) only or PBS containing 1.5, 3, or 5 mg dimethylnitrosamine (DMN)/kg body wt daily for 14 days. On Day 16, mice were evaluated for changes in immune status as measured by the antibody response to sheep red blood cells (SRBCs), blastogenesis to T- and B-cell mitogens, natural killer (NK) cell function, delayed hypersensitivity, and alveolar macrophage (AM) bactericidal activity; and for changes in host resistance following challenge with various microorganisms or tumor cells. DMN-exposed animals exhibited reduced humoral antibody responses, T-cell mitogenesis, and AM bactericidal activity. B-cell mitogenesis, NK cell activity, and delayed hypersensitivity were increased. Resistance to challenge with Listeria monocytogenes, Trichinella spiralis, or Herpes simplex types 1 or 2 virus (HSV-1, HSV-2) was not significantly impaired, while that to Streptococcus zooepidemicus and influenza virus was significantly reduced. Resistance to B16-F10 tumor challenge was enhanced following DMN exposure. The data show that DMN treatment altered humoral immunity and antibody-mediated host defense mechanisms. Increased NK cell activity may account for the increased resistance to challenge with Herpes virus and B16-F10 tumor cells.