Hygiene Hypothesis goes in utero!
On the blog and in class we have discussed the Hygiene Hypothesis. I was very interested to read today in a review article in JEM that there seems to be a growing body of evidence indicating that bacterial exposure in pregnant mothers can reduce the incidence of asthma and allergy in their children.
Of note, newborns of mothers exposed to a barn environment during pregnancy displayed enhanced Treg activity. A parallel study looking at PBMCs from 5-13 year-old children of farm-exposed mothers showed decreased sensitization. The really COOL thing is that the decreased sensitization was unrelated to the children's farm exposure at the time the PBMCs were taken. Instead the effects were exclusively related to the mothers' farm exposures during pregnancy.
This (and other data you can read in the article) suggests that during a child's development in the womb its immune system can be programmed to some degree. Why do you think maternal programming might exist? Is this exposure more relevant than the child's own exposure?
Soothing signals: transplacental transmission of resistance to asthma and allergyPatrick G. Holt and Deborah H. StricklandJ. Exp. Med. 2009;0 200924691-20092469, Published online Dec 7 2009, 10.1084/jem.20092469.
First of all, thanks for posting this article. It’s fascinating and it points at the fact that maybe we might be missing the bigger picture here when it comes to understanding the development of asthma and allergies in children.
ReplyDeleteThis topic really interests me so I found this great article published in 2005. It talks about how in utero, the maternal immune responses are dominated by TH-2/TH-reg and how TH-1 dominated responses result in a negative outcome of the pregnancy. Interestingly IFN- is extremely low in neonates and lowest in neonates with allergic mothers. Finally, it questions whether or not the dominate TH-2 response predisposes a child to allergies later in life. The article covers more than just a prenatal aspect so it’s worth reading.
Herz, Udo U (10/2005). "Perinatal events affecting the onset of allergic diseases". Current drug targets. Inflammation & allergy (1568-010X), 4 (5), p. 523.
Julie thanks for the info on that article, I'll definitely give it a read.
ReplyDeleteIt makes some sense that the mother's exposure is more important the child's as it would seem that as the immune system and organs are forming and the body is showing exogenous antigens to the immune system (to not respond to) would be the best time!
ReplyDeleteI was also very interested in this topic. Our department at Children's sponsored lectures on this specific topic, about a year ago. As a result, I took probiotics during my pregnancy to hopefully decrease the likelihood of my baby developing atopic disease.
ReplyDeleteTo play devil's advocate, here is an article showing no difference in atopy in babies born to mothers who took lactobacillus GG 4-6 weeks before expected delivery and 6 months postnatally. (this was a randomized, double-blind, placebo-controlled clinical trial) In fact, there was an increase in wheezing in the group who received lactobacillus.
Pediatrics. 2008 Apr;121(4):e850-6. Epub 2008 Mar 10.
Randomized, double-blind, placebo-controlled trial of probiotics for primary prevention: no clinical effects of Lactobacillus GG supplementation.