IMMUNOGLOBULIN (IGG AND IGA) AND COMPLEMENT (C3) CONCENTRATIONS IN UTERINE SECRETION FOLLOWING AN INTRAUTERINE CHALLENGE OF STREPTOCOCCUS-ZOOEPIDEMICUS IN MARES SUSCEPTIBLE TO VERSUS RESISTANT TO CHRONIC UTERINE INFECTION

The validity of measuring concentrations of immunoglobulins in undilut ed uterine secretions was established. The concentrations of IgG, IgA, and cleavage factor C3 of the complement system in uterine secretions were compared in mares with different resistance to chronic uterine i nfection (CUI). The uteri of mares susceptible (n = 6) and resistant t o CUI (n = 5) were inoculated with 5 x 10(6) Streptococcus zooepidemic us when the mares were in estrus. Uterine secretions were sampled, and sampling was immediately followed by a uterine lavage at 5 and 24 h a fter bacterial inoculation. During a subsequent estrus, bacterial inoc ulation of the uterus was repeated, and samples were taken from the ma res 12 and 36 h later. The fraction of uterine secretion in each uteri ne washing was determined by dividing the protein concentration of the undiluted uterine secretion by the protein concentration of the corre sponding uterine washing. There was a significant correlation between measured concentrations of immunoglobulins in uterine secretions and c alculated concentrations in the uterine washings (p < 0.05). Concentra tions of IgG and C3 in uterine secretions declined similarly in both s usceptible and resistant mares during the first 24 h after bacterial i noculation (p < 0.04). In contrast to the susceptible group, which sho wed a continuous decline at 36 h, resistant mares demonstrated an incr eased concentration of both IgG and C3 at this time. Concentrations of IgA did not differ between susceptible and resistant mares. It was co ncluded that the described method of sampling uterine secretions was u seful for analyzing IgG and IgA. Since this study was unable to detect differences in IgA, IgG, and C3 concentrations during the first 24 h of infection, the impaired uterine defense in mares susceptible to CUI is not likely to be due to local immunoglobulin deficiency.