Constitutive apoptosis in equine peripheral blood neutrophils in vitro.
Authors: Brazil Timothy J, Dixon Padraic M, Haslett Christopher, Murray Joanna, McGorum Bruce C
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary: Constitutive Apoptosis in Equine Peripheral Blood Neutrophils Neutrophil lifespan is a critical determinant of immune function and inflammatory resolution, yet programmed cell death pathways in equine neutrophils had not been systematically characterised. Brazil and colleagues cultured equine peripheral blood neutrophils in vitro for up to 36 hours, monitoring morphological and functional markers of apoptosis whilst exposing cells to various inflammatory mediators and bacterial components to identify modulating factors. Spontaneous apoptosis occurred in a time-dependent manner, paralleling patterns observed in human neutrophils, though equine cells showed species-specific responses: lipopolysaccharide and tumour necrosis factor-α accelerated apoptosis, whilst dexamethasone and complement-derived C5a protected against cell death—an effect notably different from human neutrophil behaviour with LPS. Apoptotic neutrophils retained responsiveness to direct activators (phorbol myristate acetate) but lost capacity for complement-mediated activation responses, suggesting selective functional deterioration. Understanding these apoptotic mechanisms and species differences is relevant for managing systemic inflammatory conditions, interpreting immune function tests, and potentially optimising therapeutic interventions in equine respiratory disease, colitis and sepsis where dysregulated neutrophil survival contributes to pathology.
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Practical Takeaways
- •Understanding equine neutrophil apoptosis kinetics may help explain why horses have different inflammatory responses to infection compared to humans, potentially informing treatment strategies.
- •The differential effects of corticosteroids on equine versus human neutrophil apoptosis suggests caution when extrapolating immunosuppressive therapy protocols between species.
- •Phagocytic activity promotes neutrophil apoptosis in horses, indicating that managing bacterial load and immune activation may be crucial in equine infectious disease management.
Key Findings
- •Equine peripheral blood neutrophils undergo time-dependent constitutive apoptosis in culture over 36 hours, with structural and functional features similar to those observed in human neutrophils.
- •LPS, TNF-α, and phagocytosis of opsonised erythrocytes promoted equine neutrophil apoptosis, while dexamethasone and ZAS (C5a) inhibited it.
- •Apoptotic equine neutrophils showed diminished ZAS-stimulated chemiluminescence but maintained PMA responsiveness.
- •Key differences exist between equine and human neutrophil apoptosis responses to LPS and dexamethasone, suggesting species-specific immune regulation.