Immunohistochemical study of the local humoral immune system of the equine respiratory mucosa.

The research article is about a study that used an indirect immunoperoxidase technique to identify and locate specific immune cells producing immunoglobulins (antibodies) within the mucosa of the horse’s respiratory tract.

Methodology

• The indirect immunoperoxidase technique was employed to identify and locate immunoglobulin-producing plasma cells in the mucosa of the horse’s respiratory tract. This technique uses antibodies linked to an enzyme called peroxidase, which can be visualized by reacting it with a substrate to produce a coloured product.
• The researchers were particularly interested in plasma cells – a type of immune cell – that produce three different types of immunoglobulins: IgG, IgA, and IgM. These are proteins produced by the immune system to help fight against infections.

Findings

• It was found that IgA-producing plasma cells were most prevalent in the upper parts of the airways, while IgG-producing cells were more dominant in the lower regions of the respiratory tract.
• IgM-secreting cells were the least common, but they were most present in the nasopharynx – the bodily space behind the nose that leads to the throat.
• Moreover, plasma cells that produce all three types of immunoglobulins were found, not only in the surface epithelium (the thin tissue forming the outer layer of a body’s surface), but also in the deeper connective tissue, the glandular tissue, and the organised lymphoid tissue (part of the immune system).
• The surface epithelium showed strong staining for free (unbound) IgA and IgM, but weak staining for IgG, indicating lower levels of this immunoglobulin. On the other hand, glandular cells and the connective tissue in the lamina propria (a layer of connective tissue underlying the epithelium in mucous membranes) showed the most intense staining for IgG.

Conclusion

• This study contributes to the understanding of the humoral immune response (defense mechanisms involving antibodies) in the horse’s respiratory tract by establishing the regions where specific immunoglobulin-producing plasma cells are located.
• The differences in the distribution of these cells might suggest that different parts of the respiratory tract have specialised roles in the immune response against various types of infections.