Can we predict from a blood test when someone may outgrow peanut allergy?

Teachable moment in classrooms:

1. immune system chapter – characteristics of IgG and IgE antibodies
2. immune system chapter – there are different types of white blood cells in the immune system
3. immune system chapter – some T lymphocytes secrete stimulatory chemicals called cytokines

The news item:  Recently a new report appeared online:

How antibody levels can predict which children will outgrow their peanut allergy

Australian researchers have discovered how changes in antibody levels over time can predict which children are likely to outgrow their peanut allergy.

The article reported research findings from an Australian research group, and stated that some children outgrow peanut allergies by age 6, and that following changes of two antibody biomarkers sIgG4 and sIgE in children revealed who will outgrow their peanut allergy.

So, Why Do I Care??  Allergic reaction to peanut is the most frequent allergy to food components. In the US it is estimated that between ages 6 and 10 there are over 400,000 children with peanut allergy.  As the article describes, an allergic reaction in children may set off panicking of the parents, and can endanger the life of the children. Predicting when a child may outgrow peanut allergy can mean the return to normal dietary habits of those children.

Plain English, Please!!!   First, let’s talk about what an allergy is.  Some chemicals, the allergens, have the ability to activate the T lymphocytes (T cells). Those activated T cells secrete cytokines that  stimulate mast cells to make a protein called immunoglobulin E (IgE). The cytokines act through receptors on the mast cells; so, imagine the mast cell as a soda fountain, and when you push a button on the fountain (your finger is a cytokine molecule binding to its receptor the button), a liquid comes out, the mast cell secrete IgE.  After such sensitization, when the allergen enters the body through digestion and absorption, those allergens will stick to IgE molecules and those IgE molecules bind to their receptors in the cell membrane of mast cells. The receptors, in turn, instruct the mast cells to make a chemical called histamine. Here the allergen-IgE combo is your finger, the IgE receptor is the button on the soda fountain, and histamine is flowing out of the mast cell.  Histamine spreads throughout the body, and causes coughing, tear production, sneezing, and itchy skin.

Second, let’s talk about how peanuts cause allergy. The seed of the peanut plant is rich in proteins, and some of those proteins, such as vicillins and prolamines, can bind to the IgE in the tissues of the small intestine. When that binding happens, the mast cells are sensitized as we described in the first part, and then after further exposures to peanut allergens the mast cells release large amounts of histamine. The more IgE is around, the heavier the reaction of the mast cells to peanut allergen.

Third, let’s talk about how a blood test can predict allergic response to peanuts. There are antibody types, such as the IgG antibodies, that bind to peanut allergens, but they do not stimulate mast cells. The IgG antibodies act like a mop, holding onto the allergens, and not letting them bind to IgE. The more more IgG antibodies we have, the more mopping of the allergens we do, the fewer allergen-IgE combination happens, so fewer finger are pushing the button on the soda fountain, and less histamine will be released, and the weaker will be the allergic reactions. Therefore, when you measure the IgG and IgE antibodies in blood, the higher proportion of IgG antibody marks resistance to peanut allergens, meaning that the person outgrew the allergy by increasing their IgG production.