A possible linkage between gonadal hormones, serum and uterine levels of IgG of dairy cows

We have investigated the possible linkage between serum and uterine fluid immunoglobulin G (IgG) levels and the hormonal status of the cow. In cycling cows there was a significant (P < 0.01) drop in average (of 4 consecutive days) serum IgG levels, from 36.4±6.7 mg ml−1 during the luteal phase of the estrous cycle to 28.3±5.3 mg ml−1 during and around estrus. In prepartum cows, there was a significant drop (P < 0.01) from an average of 37.6±3.7 mg ml−1 from 5 consecutive days, i.e. 11-7 before parturition, to 28.0±5.5 mg ml−1 on the day of parturition. Total IgG in the uterine fluid ranged from 30 to 115 mg in one horn and from 24 mg ml−1 to 70 mg ml−1 in the other horn during the luteal phase, but was essentially undetectable at estrus. The drop in serum and uterine IgG occurred concomitantly with the drop in peripheral serum progesterone, from 2–3 ng ml−1 at the luteal phase, and 11-7 days before calving to less than 0.5 ng ml−1 around estrus and calving. Data suggest a possible linkage between steroid hormone and IgG levels.