Immunophenotypic characterization and depletion of pulmonary intravascular macrophages of horses.

This research focuses on identifying a marker for pulmonary intravascular macrophages (PIMs) in horses, cells believed to make them more susceptible to severe reactions from endotoxins. They found that MAC-387 serves as a reliable marker and that a lanthanide group substance, gadolinium chloride (GC), can safely reduce the number of these macrophages.

Background and Objective

The researchers wanted to explore PIMs in horses, as their role was largely unknown due to past difficulties in isolating and identifying these cells. Their objective was to identify a specific marker for PIMs and establish a procedure for decreasing PIM numbers using GC, which has been demonstrated to deplete macrophages in liver and lung tissues.

Methodology

• A total of 15 horses were divided into two sets: a control group of 5 horses and a GC-treated group of 10 horses.
• Samples of lung tissue were taken from all participating animals and examined with light and electron microscopy both in ordinary and immunocytochemical settings.
• The horses treated with GC were euthanized at either 48 hours (6 horses) or 72 hours (4 horses) following treatment.

Findings

• The PIMs in the horses reacted to the MAC-387 antibody but not to the ED-1 or CD-68 anti-macrophage antibodies, designating MAC-387 as a legitimate marker for these cells.
• The researchers observed a statistically significant decrease in the number of PIMs at both 48 and 72 hours post-treatment with GC, compared to the control group.
• There was an observed increase in TUNEL-positive cells within the blood vessels of GC-treated horses, which is indicative of cellular apoptosis or programmed cell death.
• Apoptotic PIMs were observed in GC-treated horses via electron microscopy.

Conclusion

The findings suggest that MAC-387 can be used as a reliable marker for identifying PIMs in horses. Additionally, gadolinium chloride or GC is a safe and effective tool to reduce the number of these PIMs. These findings provide a foundation for further research into the role of PIMs and their contribution to the sensitivity of horses to endotoxins and may also potentially lead to the development of treatments reducing the severity of endotoxin-induced shock in horses.