For something so small and minute, dust particles can sure cause a lot of trouble. The same goes for dust mites – the tiny micro-organisms that feed on house dust, tiny flakes from human skin and moisture in the air. Together, they are some of the most common and prevalent indoor allergens present all year round.
Dust mites are active through all seasons therefore people suffering from a dust allergy are at risk of constant allergic reactions throughout the year.
Dust mites are present in almost every house around the world. There are around 13 known species of mites and all are well-adapted to our indoor environment.
Dust mites can thrive in normal room temperatures between 20 to 25 degrees Celsius and humidity of 70%-80%. These mites can be found in deep layers of furniture, bedding, carpets and even stuffed toys.
Still, many people do react with the typical allergic symptoms: sneezing, a runny nose, and itchy, swollen nasal passages. Others have a much more severe reaction: a life-threatening asthma attack.
To treat the root cause of allergies and asthma, researchers need to know exactly what sets these patients apart from healthy individuals.
In a new Science Immunology study, published on June 12, 2020, scientists at La Jolla Institute for Immunology (LJI) offer a clue to why non-allergic people don’t have a strong reaction to house dust mites.
They’ve uncovered a previously unknown subset of T cells that may control allergic immune reactions and asthma from ever developing in response to house dust mites — and other possible allergens.
“We discovered new immune cell subsets and new therapeutic opportunities,” says Grégory Seumois, Ph.D., instructor and director of LJI’s Sequencing Core and co-leader of the new study.
“This new population of cells could be one, out of many unknown mechanisms, that explains why healthy people don’t develop inflammation when they breathe in allergens.”
“The study highlights the power of unbiased single-cell genomics approaches to uncover novel biology,” says LJI Professor Pandurangan Vijayanand, M.D. Ph.D., senior author of the new study.
The study builds on the Vijayanand lab’s expertise in linking gene expression to disease development.
The team also took advantage of the Immune Epitope Database, an LJI-led resource that houses information on how the immune system interacts with allergens like house dust mites.
Why house dust mites? These microscopic critters are hard to avoid, which means nearly everyone has been exposed. Even in people without a house dust mite (HDM) allergy, the immune system is likely to react in some way as it learns to recognize HDM molecules. This makes HDM a useful model for studying what causes allergies and asthma attacks.
The LJI team used a technique part of the “genomic revolution” arsenal of tools, called single-cell RNA-seq (or single cell transcriptomics) to see exactly which genes and molecules specific T cells produce in response to HDM allergens.
They tested cells from four groups of people: people with asthma and HDM allergy, people with asthma but no HDM allergy, people with only HDM allergy, and healthy subjects.
Their analysis suggests that a subset of helper T cells, called interleukin (IL)-9 Th2 expressing HDM-reactive cells, is more prevalent in the blood of people with HDM-allergic asthma compared with those who are only allergic to HDM.
Further analysis suggested that those IL9-TH2 cells are enriched in a group of molecules/genes that increased the cytotoxic potential of those cells. In other words, those specific T cells could kill other cells and drive inflammation.