Immunologic effects of experimental iodine toxicosis in young cattle

A study was designed to evaluate effects of 4 dosage levels (0, 50, 250, or 1,250 mg) of daily iodine supplementation on cell-mediated and humoral immune mechanisms in 40 calves, 10 per group, for a 6-month period. Immune and inflammatory responses were measured by titers to brucella, leptospira, and infectious bovine rhinotracheitis virus vaccinations, by stimulation of lymphocyte mitoses with poke-weed, phytohemagglutinin (PHA), and conconavalin A mitogens, by intradermal PHA responses, by in vitro phagocytosis of Candida albicans by WBC, and by total WBC counts. Calves given 1,250 mg of iodine daily had significant (P = less than 0.05) decreases in persistence of antibody titers to brucella and leptospira organisms, in lymphocyte mitotic activity, in PHA injection induration, in phagocytosis by WBC, and in WBC counts. Calves fed iodine at 50 or 250 mg daily tended to have decreased leptospiral titers, lymphocyte mitoses, PHA injection induration, and in vitro phagocytosis by WBC compared with responses of controls. Seemingly, large amounts of dietary iodine interfere with titer maintenance to some antigens, with lymphocyte DNA synthesis, and with phagocytic activity of WBC.