Glucocorticosteroids administration is associated with increased regulatory T cells in equine asthmatic lungs.

The research study investigated the effect of glucocorticosteroids on regulatory T cells in asthmatic horses. The results showed an increase in these cells, despite continued high levels of airway inflammation.

Context of the Research

• Severe equine asthma results in a recurrent inflammation that can lead to the remodeling of the airways, causing airway obstruction which is not entirely reversible.
• Although glucocorticoids (GC), a type of steroid hormone, improve clinical signs and lung function, inflammation still persists in the airways, as evidenced by an increased percentage of white blood cells called neutrophils.
• Regulatory T cells (Treg), a type of immune cell, are known for their anti-inflammatory properties and importantly balance the immune response by suppressing the activity of effector lymphocytes.
• The interactions between Treg, neutrophils and GC are not clearly understood in asthma, specifically in in vivo conditions. Moreover, how GC affects Treg in the airway of asthmatic horses has not been explored before.

Hypothesis and Methodology

• The research team hypothesized that in horses suffering from severe asthma, there is a decreased population of Treg in the lungs compared to healthy horses. They also speculated that treatment with GC would increase the population of Treg only in horses affected by asthma.
• To investigate this, researchers conducted lung function measurements and flow cytometry using surface antigens CD4 and FoxP3 to study Treg in the airway luminal cells.
• Bronchoalveolar lavage fluid (BALF), a lung-related diagnosis tool, was collected from six asthmatic horses during an exacerbation phase and another six healthy control horses of the same age, all kept in the same environment.
• Data collection was carried out before and after a 2-week-long treatment regimen with dexamethasone, a type of GC.

Results and Implications

• The results indicated that the number of Treg increased only in the lungs of asthmatic horses following GC therapy, despite the fact that neutrophils persisted in high numbers.
• These findings highlight the complex interplay between Treg, neutrophils, and GC. The increase of Treg in response to GC treatment in asthmatic horses suggests that the immune response and inflammation in severe equine asthma are more multifaceted than previously understood.