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ORIGINAL ARTICLE: An Interleukin-23 Binding Protein in Mid-Trimester Amniotic Fluid


Steven S. Witkin, Department of Obstetrics and Gynecology, Weill Medical College of Cornell University, 525 East 68th Street, Box 35, New York, NY 10065, USA.


Problem  The binding of mid-trimester amniotic fluid to cytokines was evaluated.

Method of study  Purified tumor necrosis factor-α (TNF-α), interleukin (IL)-10, IL-12, and IL-23 were incubated with amniotic fluid from 25 women undergoing a mid-trimester amniocentesis, or with bovine serum albumin or saline, and cytokine binding to monoclonal antibodies was quantitated by ELISA. Aliquots of amniotic fluid were heated to 95°C for 15 min and then retested for IL-23 binding. The effect of amniotic fluid dilution on IL-23 quantitation was evaluated.

Results  All amniotic fluids had a negligible effect on TNF-α, IL-10, and IL-12 detection. In marked contrast, pre-incubation with amniotic fluid from each subject reduced the subsequent ability to detect IL-23 by >50%. The extent of inhibition was directly proportional to the amniotic fluid dilution and was markedly reduced following heating at 95°C for 15 min. Amniotic fluids from White, Black, Asian, East Indian, and Hispanic women were equally effective.

Conclusion  Interleukin-23 and IL-12 share a common p40 subunit and no inhibition of IL-12 was apparent. It appeared that a component of mid-trimester amniotic fluid specifically interacts with the p19 subunit unique to IL-23. Mid-trimester amniotic fluid reactivity with IL-23 may be a mechanism to limit intra-amniotic neutrophil-derived inflammation.