Serum Opsonization Capacity, Phagocytosis, and Oxidative Burst Activity in Neonatal Foals in the Intensive Care Unit

Abstract

Background: Phagocytic activity of neonatal foals has been reported to be similar to that of adult horses, but serum opsonization capacity develops with age and may be further altered when opsonins are consumed during infection.Hypothesis: Phagocytosis, oxidative burst activity, and serum opsonization capacity in neonatal foals admitted to an intensive care unit are reduced in comparison with control foals.Animals: Blood samples were collected from hospitalized neonatal foals and from control foals. Hospitalized foals were characterized as sick or septic on the basis of a sepsis score and received intravenous plasma transfusion.Methods: Phagocytosis, oxidative burst activity, and serum opsonization capacity were tested with flow cytometric analysis. Serum immunoglobulin and complement component 3 concentrations were determined with radial immunodiffusion. Serum amyloid A concentration was assayed with a commercially available solid-phase Sandwich ELISA Kit. Data were analyzed with nonparametric and regression methods. Alpha was set at P 5 .05.Results: Phagocytic functions of septic and sick foals were lower than control foals in the initial phase of the study (P 5 .01). Opsonization capacity was significantly higher when bacteria were opsonized with serum from septic (P 5 .029) and sick (P 5 .006) foals than from control foals on day 1. Opsonization capacity in septic foals was comparable with control foals on days 2 and 5. This effect was not accompanied by an increase in serum complement C3 or immunoglobulin G concentrations independently.Conclusions and Clinical Importance: Our results suggest that phagocytic function could be decreased in hospitalized foals. The synergistic effect of opsonic elements provided by plasma transfusion may sustain opsonization capacity during sepsis.

Equine Inflammatory Markers in the Twenty-First Century

“…[33][34][35][36] Foals with sepsis and other bacterial infections have significantly higher SAA concentrations than healthy foals or sick foals without inflammation, although there is enough overlap in the concentrations among these groups that SAA should not be used as a sole means of identifying infection or sepsis. [35][36][37][38] In the largest study evaluating SAA in foals, a healthy control group of 226 Thoroughbred neonates had median SAA concentrations of 0.9, 4.5, and 2.5 mg/L on 1, 2, and 3 days old, with the values on Day 2 being significantly higher than on Day 1. 33 In 136 foals with clinical disease, median SAA concentrations of cases with focal infections (eg, omphalitis) were 195 mg/L and those with septicemia higher still at 280 mg/L.…”

Transfer of tumour necrosis factor‐α via colostrum to foals

“…However, even with sufficient IgG absorption, equine neonates are still susceptible to a variety of pathogens that rarely affect adult horses, including Rhodococcus equi , rotavirus, Cryptosporidium parvum , Pneumocystis carinii and Candida albicans (Boyd and others 2003, Horohov and others 2006). Importantly, sick foals and foals with sepsis have a lower phagocytic function than the healthy foals, which may affect their ability to kill pathogens; nevertheless, when supplemented with plasma products intravenously, they sustain comparable opsonisation capacity to healthy foals (Gardner and others 2007).…”

“…Foals begin to develop their innate and adaptive immune functions partially during gestation, but more significantly after birth when exposed to environmental organisms (Flaminio and others 2000, Boyd and others 2003, Holznagel and others 2003, Gardner and others 2007, Tallmadge and others 2009). The previous in vitro experiments using peripheral blood mononuclear cells isolated from equine neonates have shown cytokine responses upon stimulation comparable with older foals and adult horses (Flaminio and others 2009).…”

Neutrophilic myeloperoxidase index and mean light absorbance in neonatal septic and nonseptic foals

“…Another possible explanation is that higher values for MPXI in septic/neutropenic foals compared with other sick foals might reflect a lack of neutrophil activation/degranulation and, possibly, reduced neutrophil function. In hospitalized septic foals, phagocytosis, and oxidative burst activity have been shown to be decreased 16,17 . Similarly, reduced neutrophil function has been observed in septic dogs and people 18,19 .…”

“…Investigation of concurrent changes in plasma and intracellular myeloperoxidase activity would help to further clarify dynamics of neutrophil activation and degranulation. Comparison with other tests, such as flow cytometric analysis for expression of CD11 and CD18, serum opsonization capacity, phagocytosis, and oxidative burst activity, would also assist in determining the value of MPXI and NXM as markers of neutrophil function 14,16,17 …”