Chronic small airway disease in the horse: immunohistochemical evaluation of lungs with mild, moderate and severe lesions.

The study investigates the occurrence and varying levels of immunoglobulins (a type of protein that plays a key role in immune responses) in the lungs of horses suffering from chronic small airway disease. It reveals a correlation between the severity of the disease and the presence of these proteins.

Objectives and Methodology

• The research aims to understand chronic bronchiolitis or small airway disease in horses, by examining the presence and pattern of immunoglobulins, which are essential parts of the immune response.
• The researchers used a method known as the peroxidase anti-peroxidase technique. This technique helps detect and measure the presence of specific proteins (in this case immunoglobulins) within a sample.
• The samples for this study were the lungs retrieved from 23 horses diagnosed with chronic small airway disease, and their severity was classified into mild, moderate, and severe based on the extent of bronchiolitis.
• Three healthy horses without any pathological changes in their lungs were used as control subjects.

Findings

• The study found a correlation between the extent of bronchiolitis and the presence of immunoglobulins. Horses with mild bronchiolitis showed an increased number of IgA (a class of immunoglobulin) containing cells and other non-immunoglobulin cells around their vasculature and bronchioles when compared to the control horses.
• As the severity of the disease increased, so did the number of different types of immunoglobulins (IgA-, IgG(Fc)-) and in several cases, other non-immunoglobulin cells, particularly around the vasculature, bronchioles, and within the septa that divide the alveoli (tiny air sacs in the lungs).
• In severely affected horses, there were large quantities of free IgG(Fc), another type of immunoglobulin, found in the spaces between tissues (interstitially) and inside the alveoli.
• In certain areas where the mucosal epithelial cells (the cells lining the bronchioles and alveoli) showed abnormal proliferation (hyperplasia) or transformation into different types of cells (metaplasia), large amounts of free IgA and IgG(Fc) were observed within and between the epithelial cells. This pattern differed notably from those seen in the control horses.

Implications

• Suggesting the immune response of horses to chronic small airway disease, the study can pave the way for novel therapeutic approaches that may influence these responses.
• The distinct presence and pattern of immunoglobulins could also potentially be used as markers to diagnose the severity of this disease in horses.