Suppression of immune response in lambs during treatment with the beta-adrenergic agonist clenbuterol.

The effect of the beta-adrenergic agonist clenbuterol on immune function was examined in sheep. Twenty ewe lambs were housed indoors, with food and water available on an ad libitum basis, and immunized against somatostatin (SRIF) using a SRIF-ovalbumin conjugate. Ten of the lambs were also treated with clenbuterol (400 micrograms/kg) each day; 10 controls were not treated. After 5 wk of treatment (with booster injections of the SRIF conjugate each fortnight), the lambs were bled and then slaughtered for carcass composition. The lambs that received immunization alone produced significant antibody titers against SRIF, whereas 9 of the 10 clenbuterol-treated lambs produced no significant, specific antibody response. There was no effect of clenbuterol treatment on liver, thymus, spleen, kidney, kidney fat, or biceps femoris weight compared with those lambs that were only immunized. These results indicate that treatment with clenbuterol may inhibit humoral antibody response to infection.