A new way to look at house dust mite allergy and avoidance

To make it easier to understand the origins of allergy and allergic reactions, doctors have devised a simple two-tiered framework. They have divided immune reactions into adaptive and innate responses. In doing this they have also made it easier for allergy patients to understand the problem.

The term adaptive refers to the activity of defense cells known as T and B lymphocyte cells. These are the immune cells that are influenced by genetic signals and are called ‘adaptive’ because they can change with environmental exposure and in time. T cells come from the thymus while B cells are made in bone marrow; both are associated with long-term memory of environmental harm to the body either perceived or actual.

Innate refers to cells throughout the body that are known to respond quickly to infections or tissue injury, but have limited capacity for long-term memory, a fact that is important in mite allergen avoidance! In the respiratory tract epithelial and dendritic cells are prime examples of how innate cells work.

Epithelial cells form the protective barrier of the lungs and continually ‘test’ the air breathed in while sweeping clean unwanted debris. If damaged they can send out danger signals before being replaced. Underneath the epithelial barrier, and located in delicate tissue, are dendritic cells. These are clean-up cells ready to warn of an invasion that has breached the epithelial barrier. They are important in allergy because they can be the first to recognize a potential allergen and respond by signaling T adaptive cells of potential danger. Once alerted, dendritic cells can bristle with sensors primed to identify specific targets, such as allergens from house dust mites.

All innate cells respond quickly and are capable of triggering a cascade of immune reactions that, in allergy, are known as allergic reactions. The good news is that their lack of long-term memory helps to make allergen avoidance work in allergic disease management.

In the published report used as the basis of this article the authors describe the dust mite enzyme (Der p1) as ‘dangerous’, because Der p1 can act to skew an immune response towards both adaptive and innate immune reactions. The authors also note that the dust mite allergen (Der p2) has the ability to mimic an ancient innate immune response, a component of TLR4 complex, and must do this in order to function. This is why the authors refer to Der p2 as a ‘bad actor’. Why is this interesting? The TLR4 complex noted is linked to immune sensitization [potentially leading to allergy], as noted in the article.

References

'Dangerous Allergens: Why Some Allergen are Bad Actors'
Georas SN, Fezaee F, Lerner L , Beck L, 'Curr. Allergy Asthma Rep.' 2010, 10: 92-98