Human mid-gestation amniotic fluid contains interleukin-16 bioactivity

C. Thornton, J. Holloway, Jan Shute, John W. Holloway, N. Diaper, J. Warner

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CD4-positive cells are detectable in the human fetal gastrointestinal tract from 11 weeks of gestation. Interleukin-16 (IL-16) is a chemoattractant for CD4(+) cells and, via fetal swallowing of amniotic fluid, could mediate the influx of CD4(+) cells into the fetal gut. We have shown that IL-16 was detectable in human amniotic fluid at 16-18 weeks of gestation (mid-pregnancy) but was not detectable at term (late pregnancy; > 37 weeks of gestation). Similarly, mid-pregnancy, but not late pregnancy, amniotic fluid contained chemotactic activity for CD4(+) T cells, this activity was reduced by 58% in the presence of a neutralizing anti-IL-16 antibody. The levels of IL-16 in fetal plasma at 16-24 weeks of gestation were very high, and decreased significantly by 25-36 weeks but at > 37 weeks remained significantly higher than adult levels. IL-16 transcripts were detectable in whole tissue extracts of fetal gut, skin and placenta but not in amniocytes, and IL-16 immunoreactivity was detectable in cells within the lamina propria of the fetal gut and within the skin, where it was associated with the basement membrane. Neither IL-16 levels nor chemotactic activity for CD4(+) T cells in mid-pregnancy amniotic fluid was related to atopic outcomes at 1 year of age. IL-16 might have an important role in the early development of the human immune system and/or in regulating fetal and maternal immunological responsiveness during pregnancy.
Original languageEnglish
Pages (from-to)543-551
Number of pages9
Issue number4
Publication statusPublished - Apr 2009


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