• -Natalie

Role Played by Th2 type Cytokines in IgE Mediated Allergy & Asthma

This study (referenced at the bottom of this article) discusses the role played by Th2 type cytokines in IgE mediated allergic reactions. Let's first define Th2 cells and cytokines.

Th2 is short for type 2 helper T cells. These are a type of lymphocyte that secrete various cytokines (IL-4, IL-5, IL-6, IL-13). You can think of cytokines as small proteins that tell other cells what to do. IL stands for interleukin, which is a type of cytokine. In addition to releasing various cytokines, these Th2 cells regulate B cell and eosinophil mediated responses.

Why should we care about these Th2 cells? Evidence suggests that Th2 cells play a role in the activation and recruitment of IgE antibody producing B cells, mast cells and eosinophils. Basically, they play a role in sensitization to food allergens. Mast cells and eosinophils both play an important role during anaphylaxis.

But why do these Th2 cells even activate IgE antibody producing cells in the first place? You see, our immune system is tightly regulated, and two major components of our immune system: type 1 helper T cells and type 2 helper T cells are kept in balance.

Th2 cells are responsible for activating cells that actually have an anti-parasitic role in our immune system. Mast cells, eosinophils, basophils and IgE antibodies all target parasites (think worms). But in today's developed world, especially in first world countries, we don't encounter parasites very often, if at all, so these cells have kind of "lost their way".

When the Th1/Th2 balance is thrown off towards a Th2 dominance, we begin to experience allergic diseases. You're probably wondering: how does it become unbalanced?

It has been found that reduced microbial exposure early in life is responsible for a shift in the Th1/Th2 balance of our immune system towards the pre-allergic Th2 response. But we still don't know if reduced microbial exposure is the only environmental factor influencing this Th1/Th2 immune effect.

But is the Th1/Th2 balance the only immune system dysregulation involved in allergy? Not so fast. Remember that I summarized another study all about regulatory T cells playing a role in allergic disease as well. This study builds on the last one mentioning that material regulatory T cells actually has an affect in the feto-maternal relationship.

So what is the conclusion? The Th2-skewed immune response is due in part by a reduction in regulatory T cells cytokines and a reduction of Th1 cytokines due to improved hygiene (which then leads to a Th2 dominant immune response) AND the reduced microbial exposure in early life.

The study focused on the specific cytokines in healthy patients versus in patients with various allergies. It was found that the levels of IL-4, IL-5 and IL-6 (which are all secreted by Th2 cells) were not significant between groups, BUT the levels of IL-10, IL-13 and TNFa were highly significant between groups!

You can measure your interleukin levels with a simple blood test, usually referred to as a cytokine panel.

Now, if only we could figure out how to maintain the Th1/Th2 balance to begin with, right?

Title: Role played by Th2 type cytokines in IgE mediated allergy and asthma

Authors: Sudha S. Deo, Kejal J. Mistry, Amol M. Kakade, and Pramod V. Niphadkar

doi: 10.4103/0970-2113.63609

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