Immunosuppressant activity of aflatoxin ingestion in rabbits measured by response to Mycobacterium bovis antigen I. Cell mediated immune response measured by skin test reaction.

Thirty New Zealand 2-mo-old rabbits were divided into 5 groups. Groups 1 and 2 were fed 2 ppm aflatoxin B1 daily for 5 w before sensitization and continued for another 7 w. Groups 1 and 3 were infected with Bacillus of Calmette and Guerin while groups 2 and 4 were sensitized with killed cells of Mycobacterium bovis. Group 5 did not receive any treatment (control). Citrated whole blood samples were collected from all groups before treatment and at 5, 8 and 12 w during the experiment. The lymphoblastogensis assay was done presensitization and at 3 and 7 w post-sensitization for all groups. The lymphocyte stimulation indices and diameter of skin reactions were significantly reduced in the aflatoxin-treated groups (P < 0.001). In addition, 3/12 rabbits (25%) from the aflatoxin groups (groups 1 and 2) failed to produce any detectable response to the tuberculin test. Aflatoxin inhibited lymphocyte proliferation and negatively influenced the tuberculin skin test.