Human mid-gestation amniotic fluid contains interleukin-16 bioactivity.
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.
Thornton
Catherine A
CA
Institute of Life Science, School of Medicine, Swansea University, Swansea. c.a.thornton@swansea.ac.uk
Holloway
Judith A
JA
Shute
Janis K
JK
Holloway
John W
JW
Diaper
Norma D
ND
Warner
John O
JO
D000653:Amniotic Fluid / Q000276:immunology*; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D002634:Chemotaxis, Leukocyte / Q000276:immunology; D005333:Fetus / Q000276:immunology; D005865:Gestational Age; D006801:Humans; D006969:Hypersensitivity, Immediate / Q000196:embryology / Q000276:immunology; D007223:Infant; D019410:Interleukin-16 / Q000378:metabolism*; D007422:Intestines / Q000196:embryology / Q000276:immunology; D012867:Skin / Q000196:embryology / Q000276:immunology
D019410:Interleukin-16