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Early infection and protection against allergies?
23 June 2009
When infected, the body has two types of immune defence to deploy – innate immunity and acquired immunity. In her dissertation, Shanie Saghafian Hedengren studies monocytes, a type of white blood corpuscles that are part of the innate immune system.
“Innate immunity plays a crucial role at the beginning of life as protection against bacteria and other microbes, since the acquired immune system is not fully developed at that stage. What’s more, acquired immunity and its memory are formed by ‘communication molecules’ that are initially transmitted by monocytes, among other sources. Imbalance in the monocyte function, as a result of less stimulation by microbes and viruses early in life, may therefore play an important role in the development of allergies,” maintains Shanie Saghafian Hedengren.
In this dissertation, a group of children is followed from birth to the age of five years. It shows the correlation between Epstein-Barr virus (EBV) contraction before the age of two and a lower risk of producing antibodies against allergens, so-called allergic sensitization. It is also of interest that EBV infection after the age of two was correlated with a greater risk of sensitization in five-year-olds.
EBV is a common herpesvirus that the majority of the world’s population carry throughout their lives. It is a highly successful virus that is normally spread via saliva and infects people early in life. Most people hardly notice when their children become infected.
“Contracting EBV later in life can lead to glandular fever, and apace with greater affluence, increased numbers of glandular fever cases have been reported. Perhaps from an evolutionary perspective it is more advantageous for both the virus and its host to meet earlier in life,” says Shanie Saghafian Hedengren.
The dissertation shows that the innate immunity in EBV-infected children also reacts in a mitigated way, which may explain why early infection normally produces no symptoms. These findings contradict the accepted view that what we might expect in this group with a lower risk for sensitization. Further, Shanie Saghafian Hedengren shows that newborn children have weaker monocyte responses to microbes up to the age of two if they have an allergic mother.
“Nevertheless, these high-risk children need adequate immune stimulation early in life in order to reduce the risk of allergies. In other words, lots of love for the youngest babies in the form of many and sloppy kisses,” concludes Shanie Saghafian Hedengren.
Dissertation title: Microbial and maternal influences on allergic sensitization during childhood: defining a role for monocytes.