Special cell signature predicts asthma susceptibility

It has come to light that a special type of cells and their frequency can help predict asthma susceptibility.

According to a La Jolla Institute for Allergy and Immunology research, a special subset of T cells have been identified, whose frequency serves as early childhood immune signature that predicts the risk of developing asthma later on.

"We found what I would consider very strong biomarkers for those children who are most likely to develop asthma as they get older," said senior author Mitchell Kronenberg.

The team's findings indicated that the presence of house dust components that stimulate the innate immune system decreases asthma risk, increased microbial exposure in the first years of life is protective for asthma, going consistently with the "hygiene hypothesis".

Kronenberg added, "We are not advocating for dirt and we don't know enough about the microbiome to know which aspects are beneficial but as we learn more it is feasible that one day the protective components could even be taken in pill form".

Initiated in 2005, the study follows 560 families from four disadvantaged urban areas that were at high risk for asthma to uncover potential risk factors that contribute to increased asthma rate in children growing up in impoverished neighborhoods.

Postdoctoral researcher and co-first author Shilpi Chandra and her colleagues were particularly interested in MAIT cells (short for mucosal-associated invariant T cells) and their brethren, invariant natural killer T (iNKT) cells.

Both cell types are an integral part of the innate immune response, which reacts almost immediately to foreign invaders.

"Children who, at the age of one, had a higher frequency of so-called MAIT cells appear to be less likely to develop asthma by the age of seven", Kronenberg added.

Unlike conventional T cells, which belong to the adaptive arm of the immune response and take a few days before they are fully trained on a single, specific protein fragment or peptide antigen, MAIT and iNKT cells recognize molecular components common to many microbes.

The team analysed the frequency of different types of immune cells in blood collected from 110 one-year-old study participants, the presence of immune-stimulatory components in the subjects' house dust and asked whether any of the factors correlated with an increased of asthma at age seven.

"We found certain immune signatures such as having more MAITs that are protective," said Chandra. "In humans, MAIT cells are unique in that they are borne to make gamma interferon, which could help skew the immune system toward an asthma-protective Th1 immune response."

And while the absolute numbers of iNKT cells had no bearing on asthma risk, the iNKT cell antigenic content in house dust from subjects' houses did.

Chandra concluded, "iNKT activity reflects a home environment with increased microbe exposure and therefore protection from asthma".

The study is published in the online edition of the Journal of Immunology.