In vitro and in vivo interferon production by bovine colostral leukocytes

Sixteen healthy pregnant cows were divided into two groups. Group I (8 cows) received immediately after calving two injections of Vaccina L containing the LaSota strain of Newcastle Disease Virus (total dose 10(9) TCID50/cow) into udder lymph nodes. The second group of 8 cows served as control. Newborn calves of both groups of cows were allowed to suckle the colostrum. Interferon activity was detected 24 h after injection in whey obtained from colostrum of Vaccina L-treated dams and in supernatants of cultures of colostral leukocytes. Interferon was also present in sera of Vaccina L treated dams 48 h after injection. No IFN activity was detected in sera of calves. Cultures of leukocytes obtained from colostrum of dams 48 h after Vaccina L-treatment exhibited hyporeactivity to the second induction in vitro and produced low IFN levels in response to NDV. In contrast to hyporeactivity observed in colostral leukocytes, peripheral blood leukocytes (PBL) of calves suckling colostrum from dams treated with Vaccina L produced higher IFN levels after induction in vitro with NDV than leukocytes of control calves.