Stimulation of maternal anti-lymphocyte antibodies by first gestation bovine fetuses.

Serum samples were taken from first-calf dairy heifers, twice weekly, for a period of 4 weeks, starting 2 weeks before the estimated date of parturition and continuing for 2 weeks post partum. Samples from each heifer were incubated with lymphocytes from the respective calf when possible, and from a 36-cow donow panel, in the presence of complement. Of the 31 heifers tested, 11 (35%) raised detectable lymphocytotoxic antibodies against fetal antigens; 3 had detectable, but weak, antibody titres as early as 10 days before parturition while the others had stronger antibody reactivity which was detectable 4--12 days post partum. The titres of these post-partum antibodies peaked 4--7 days after they were first detected. Sephadex G-200 fractionation of the sample taken at 2 weeks post partum showed that 11 responding cows had antilymphocytic activity in the IgG fraction while 8 also had IgM antibody activity.