Serum opsonization capacity, phagocytosis, and oxidative burst activity in neonatal foals in the intensive care unit.
Authors: Gardner Rachel B, Nydam Daryl V, Luna Jennifer A, Bicalho Marcela L S, Matychak Mary Beth, Flaminio M Julia B F
Journal: Journal of veterinary internal medicine
Summary
# Editorial Summary: Immune function in hospitalised neonatal foals Neonatal foals admitted to intensive care demonstrate significantly impaired phagocytic activity and oxidative burst capacity compared with healthy age-matched controls, raising questions about their ability to mount effective innate immune responses during critical illness. Using flow cytometric analysis, researchers measured phagocytosis, oxidative burst activity, and serum opsonization capacity in hospitalised (septic and sick) versus control foals, alongside immunoglobulin, complement C3, and serum amyloid A concentrations. Septic and sick foals showed substantially reduced phagocytic function initially (P = 0.01), yet paradoxically demonstrated higher opsonization capacity on day 1 compared with controls—an effect that equalised by day 5—despite no independent elevation in complement C3 or IgG. The elevated early opsonization capacity in sick foals likely reflects compensatory mobilisation of existing opsonic elements, with plasma transfusion helping to sustain this capacity during the critical septic phase before natural recovery occurred. These findings suggest that immune assessment should factor in both functional deficits *and* compensatory responses in hospitalised neonates, potentially informing decisions around plasma transfusion protocols and timing of antimicrobial or immunomodulatory interventions in foal intensive care.
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Practical Takeaways
- •Neonatal foals admitted to ICU have compromised innate immune function (reduced phagocytosis and oxidative burst) compared to healthy foals, indicating greater susceptibility to infection complications
- •Plasma transfusion in sick and septic foals appears to enhance opsonization capacity through synergistic effects of multiple opsonic elements, supporting its use in neonatal sepsis management
- •Early recognition of immune dysfunction in hospitalized neonatal foals is important as serum opsonization capacity declines after day 1, potentially limiting the protective benefits of endogenous opsonic activity
Key Findings
- •Phagocytic function and oxidative burst activity were significantly lower in septic and sick hospitalized foals compared to control foals in the initial phase (P = .01)
- •Serum opsonization capacity was paradoxically higher in septic (P = .029) and sick (P = .006) foals on day 1, but normalized by days 2-5
- •Increased opsonization capacity in sick foals was not explained by elevated serum complement C3 or immunoglobulin G concentrations alone, suggesting a synergistic effect from plasma transfusion