Opsonins of Streptococcus in uterine flushings of mares susceptible and resistant to endometritis: control of secretion and partial characterization.

The release of opsonins into the uterine lumen of mares susceptible or resistant to endometritis was examined after intrauterine inoculation of a filtrate of Streptococcus culture fluid or vehicle. Uterine flushings were collected at 0.5 hour before and 2, 4, 6, 8, and 24 hours after inoculation on day 2 or 3 of estrus and on day 7 or 8 after ovulation. Amounts of opsonins in flushings were quantified as the H2O2 produced by leukocytes incubated with flushings-opsonized bacteria, compared with H2O2 produced by leukocytes incubated with nonopsonized bacteria. Opsonin values in flushings increased (P less than 0.025) in all mares after inoculation of filtrate or vehicle. For mares resistant to endometritis, opsonin values were greater at diestrus than at estrus. The opposite was true for mares susceptible to endometritis, resulting in a status (susceptible vs resistant) X stage of cycle interaction (P less than 0.025). Overall, opsonins were higher (P less than 0.05) in flushings of mares susceptible to endometritis than in flushings of mares resistant to endometritis, but this difference was only apparent at estrus. Preliminary characterization of opsonins in uterine secretions by ammonium sulfate fractionation and gel filtration indicated that opsonins were mainly associated with an ammonium sulfate-soluble fraction of high molecular weight (greater than 4 X 10(6] and an ammonium sulfate-precipitable fraction that was associated with immunoglobulin G.