Researchers at McGill University Health Center ( MUHC ) discovered that our body's own defense mechanism causes some of the most serious asthma symptoms.

The study, published in the Journal of Clinical Investigation ( JCI ), reveals that T lymphocytes are responsible for the airway thickening, which increases the chances of a dangerous asthma attack.

The discovery provides hope that new treatments might be developed to combat the disease, which currently has no cure.

Asthma symptoms are triggered by two factors: inflammation of the airways in the lungs, and thickening of airway muscle in the bronchi--an irreversible condition that doctors refer to as airway remodeling.
Certain allergens--commonly dust and animal hair--can trigger inflammation, but the causes of airway remodelling, and the link between the two, have remained a mystery.

MUHC researchers have now discovered that remodeling is actually caused by T lymphocytes.

" T lymphocytes are the traffic cops of the cellular world," says Ramos-Barbón. Where antigens are present, T lymphocytes can be found directing the body's defense mechanism, which in the case of asthmatics results in airway remodeling.
" This is a natural response designed to protect the body from disease," notes Ramos-Barbón. "But in this case it actually promotes conditions that favour asthma, leading to increased symptoms such as coughing and difficulty breathing.

To make their discovery, researchers at the MUHC removed T lymphocytes from asthmatic rats, made them fluorescent by adding a jellyfish gene, and then transplanted them into non-asthmatic rats.

" The fluorescence allowed us to track the movement of the T lymphocytes and determine their effect on the non-asthmatic rats," says Ramos-Barbón.

Researchers were surprised to discover that the T lymphocytes moved directly to--and infiltrated--the airway walls of the non-asthmatic rats, causing extensive remodeling. Moreover, researchers discovered that the T lymphocytes must be in direct contact with the cells of the airway wall in order to cause remodeling.

" This discovery is particularly exciting because it provides insight as to how the body's own CD4 T lymphocytes cause the thickening of the airway muscle, which increases the chances of a dangerous asthma attack. This research opens up new ways to prevent and treat asthma and its complications," said Bhagirath Singh, Scientific Director of CIHR's Institute of Infection and Immunity.

Source: McGill University, 2005


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