Immune responses and plasma hormone concentrations in cold-exposed, xeranol-implanted calves

Hormonal involvement in the regulation of immune events was studied by exposing calves to cold air (-15 C) for 12 hours or by implanting animals with a growth promotant (xeranol) that is known to affect plasma hormone concentrations. Cold exposure significantly reduced serum IgM concentration by 23%, increased expression of tuberculin reactions to purified protein derivative by 60%, and augmented contact-sensitivity reactions to dinitrofluorobenzene by 31%. There was also a significant increase in plasma cortisol and insulin values and a reduction in growth hormone and prolactin values in cold-exposed calves. The cold-induced increase in contact reactions and plasma insulin was higher in xeranol-implanted calves, but the increase in plasma cortisol concentration caused by cold exposure tended to be reduced by the xeranol treatment. These data demonstrate that cold exposure alters immune reactions of calves and that these changes in immune events are associated with changes in a variety of plasma hormones. These results also indicate that it may be possible to augment immune reactions in vivo by appropriate hormonal modulation.