Qualitative variation in the immune response to ovarian follicular fluid proteins in cattle

In two experiments 44 heifers were immunised with inhibin preparations of partially purified ovarian follicular fluid (PPFF) of ovine, porcine and equine origin in non-ulcerative Freund's adjuvant. In the first experiment 20 cattle were immunised with ovine PPFF1. In the second, a further 24 were immunised with either a different sheep PPFF (ovine PPFF2) or PPFF from pigs or horses. Large molecules of over 30 kDa initiated a strong immune response in some animals, but none in others, although there was no obvious relationship with the MHC Class I (BoLA) phenotype. Immunisation with ovine partly purified follicular fluid affected ovulation rate in some cattle, and only these cows produced detectable antibodies to an approximately 40 kDa protein. These data show that the immunological response of cattle to a mixture of antigens is highly variable between individuals and may explain the variation in the ovarian response to immunological manipulations of ovulation rate seen in this species.