Cellular and humoral immunity in chronic equine laminitis.

The research investigates the immune responses related to chronic equine laminitis, an inflammatory disease that causes consistent pain and impaired mobility in horses. The study did not find supporting evidence of an autoimmune component in the illness, but suggests neutrophils might be involved in contributing to the inflammation and tissue damage.

Investigation of Immune Responses in Equine Laminitis

• The study was conducted to explore the hypothesis that chronic equine laminitis might involve an autoimmune response. Equine laminitis is a chronic inflammatory disorder that causes severe pain and restricted movement in horses, often leading to euthanasia due to ineffective pain management.
• Researchers investigated this hypothesis by examining various immune indicators in healthy horses (CON) and horses suffering from chronic laminitis (LMN).

Higher IFNγ in Laminitic Horses

• It was observed that white blood cells from LMN horses produced more IFNγ (Interferon gamma) compared to the CON horses when stimulated in vitro with polyinosinic-polycytidylic acid [poly(I:C)], potentially due to an increased number of circulating monocytes – a type of white blood cell.

Similar Plasma Concentrations

• There were no observable differences in the plasma concentrations of various types of antibodies (IgG, IgA, IgM, IgE) or rheumatoid factor between the CON and LMN horses. These elements play significant roles in immune system responses.

Elevated Indicators of Damage in Laminitic Horses

• Laminar tissue, a part of the horse’s hoof affected by laminitis, from LMN horses showed increased levels of genes associated with keratinocyte damage. Keratinocytes are the main cell type in the skin’s outer layer.
• The same tissue also showed elevated levels of inflammatory cytokines – small secreted proteins released by cells – and chemokines, which are a specific family of cytokines. These are known to coordinate inflammation and immune responses.
• This corresponded with a noticeable amount of neutrophil infiltration, as shown by staining fixed tissue and accumulation of neutrophil elastase protein. Neutrophils are a type of white blood cell that responds quickly to inflammation.

No Autoimmune Component but Possible Neutrophil Involvement

• Despite the investigation, the results did not support the hypothesis that an autoimmune component is associated with chronic laminitis. However, the significant induction of chemokines that attract neutrophils and the presence of these cells in the tissue suggest that they might play a role in the continued inflammation and tissue damage connected with the disease.