Chil­dren’s food al­ler­gies re­lated to im­muno­sup­pres­sion Sover

Pakistan Observer - - KARACHI CITY -

CIENTISTS have found new ev­i­dence to ex­plain how food tol­er­ance emerges

time in nor­mal in­di­vid­u­als, ac­cord­ing to re­search pub­lished in Sci­ence. Food al­ler­gies af­fect around 15 mil­lion Amer­i­cans, in­clud­ing many chil­dren. Symp­toms of al­ler­gies and in­tol­er­ance can range from rel­a­tively mi­nor, such as a harm­less skin rash, to po­ten­tially fatal ana­phy­lac­tic shock. Many in­di­vid­u­als out­grow their al­lergy as they reach adult­hood. This is thought to be due to the im­mune sys­tem learn­ing to tol­er­ate food that it pre­vi­ously per­ceived as “for­eign.”

Re­searchers from La Jolla In­sti­tute for Al­lergy and Im­munol­ogy (LJI) in San Diego, CA, led by Charles Surh, PhD, wanted to ex­plain why chil­dren, who have more lim­ited ex­po­sure to novel foods than adults, are more prone to food al­ler­gies. They hy­poth­e­sized that con­sum­ing a nor­mal diet would stim­u­late cells in the gut that pre­vent the im­mune sys­tem from re­ject­ing food. Food and pathogens both dis­play macro­molec­u­lar mark­ers known as anti­gens. These anti­gens an­nounce to the im­mune sys­tem that a food is “for­eign.”

Mouse stud­ies have pre­vi­ously looked at how the body would dis­tin­guish anti­genic “friend” from “foe.” The mice were fed with an egg pro­tein that they had not eaten be­fore. Re­searchers ob­served that an im­muno­sup­pres­sive cell, called a Treg cell, was pro­duced in the gut. These Treg cells blocked the im­mune re­sponse to the new sub­stances. It was not known if this would hap­pen when young mam­mals en­coun­tered new foods in “real life.” Surh used “anti­gen-free” mouse mod­els to rep­re­sent an im­muno­log­i­cal blank slate. The mice were raised in a germ-free en­vi­ron­ment. They were also fed a diet of amino acids, the build­ing blocks of pro­teins, in­stead of foods that con­tain the pro­teins them­selves.

This made the mice “im­muno­log­i­cally naïve,” be­cause amino acid build­ing blocks are not big enough for the im­mune sys­tem to rec­og­nize them. It meant that the mice had lit­tle or no pre­vi­ous con­tact with anti­genic pro­teins and other macro­molecules. Other mice were germ free but fed on a nor­mal diet. Molec­u­lar marker anal­y­sis re­vealed that the mice that con­sumed amino acids had no Tregs in the small in­tes­tine. In con­trast, mice that were fed a nor­mal pro­tein diet had a large num­ber of Tregs. This sug­gests that when pro­teins are con­tained in food, they stim­u­late Treg de­vel­op­ment. It also in­di­cates that Tregs in the gut of nor­mal mice might serve to pre­vent a po­ten­tially dis­as­trous im­mune re­sponse to those pro­teins.

The re­searchers also demon­strated that food and ben­e­fi­cial bac­te­ria in the gut gen­er­ate dif­fer­ent types of Tregs. Germ-free mice ap­pear to have only food-de­pen­dent Tregs and lack the kind of Tregs that are in­duced by healthy mi­crobes. These mice are also known to be very sus­cep­ti­ble to al­ler­gies. The sci­en­tists de­duced that to pre­vent al­ler­gic symp­toms, the gut needs both food- and mi­crobe-in­duced Tregs.

Newspapers in English

Newspapers from Pakistan

© PressReader. All rights reserved.