Effects of equine SALSA on neutrophil phagocytosis and macrophage cytokine production.
Authors: Lee Gary Kwok Cheong, Kang Heng, Beeler-Marfisi Janet, Sears William, Lillie Brandon N, Bienzle Dorothee
Journal: PloS one
Summary
Salivary scavenger and agglutinin (SALSA) is known to modulate immune responses in humans, but its role in equine immunity has remained poorly characterised. Kwok Cheong and colleagues investigated SALSA's effects on two key immune functions by purifying the protein from equine duodenal tissue and testing its impact on neutrophil bacterial phagocytosis using whole blood from seven horses, and on pro-inflammatory cytokine production from alveolar macrophages isolated from five horses challenged with lipopolysaccharide. Counter-intuitively, the highest SALSA concentration (20 µg/mL) suppressed neutrophil phagocytosis compared to lower concentrations or controls, whilst SALSA significantly reduced production of the pro-inflammatory cytokines IL-8, TNF-α, and CXCL1, yet paradoxically increased G-CSF production by activated macrophages. These anti-inflammatory effects suggest SALSA may interfere with toll-like receptor signalling and point to a novel immunoregulatory pathway in the equine respiratory tract, with potential implications for managing airway inflammation and understanding why salivary components may offer protective effects during stress or infection. The concentration-dependent suppression of phagocytosis warrants further investigation to clarify whether physiological SALSA levels enhance or inhibit bacterial clearance in vivo.
Read the full abstract on PubMed
Practical Takeaways
- •SALSA may have anti-inflammatory properties in horses through modulation of macrophage cytokine responses, potentially relevant to managing systemic inflammation and respiratory conditions
- •The dose-dependent effect observed suggests that optimal therapeutic concentrations matter—higher concentrations do not necessarily provide greater benefit and may be counterproductive for phagocytosis
- •Further in vivo studies are needed before clinical application; these are fundamental immunology findings that establish biological plausibility for future therapeutic exploration
Key Findings
- •SALSA at 20 µg/mL significantly reduced neutrophil phagocytosis compared to lower concentrations (10 and 2.5 µg/mL) at 37°C
- •SALSA plus LPS reduced pro-inflammatory cytokines (CXCL1, IL-8, IL-10, TNF-α) in equine alveolar macrophages compared to LPS alone
- •SALSA treatment increased G-CSF production in macrophages, suggesting a novel immunoregulatory mechanism in horses
- •SALSA demonstrates dose-dependent and temperature-dependent effects on immune cell function in vitro