Neutrophil functions and serum IgG in growing foals

Abstract

Summary The aim of this study was to investigate the phagocytic and killing capacities as well as expression of CD18 of neutrophils obtained from healthy foals from birth to age 8 months. Blood was taken from 6 Standardbred foals at 7 time‐points between ages 2–56 days and thereafter once a month. For comparison, cells from 16 mature horses were evaluated. Neutrophil phagocytosis of yeast cells was assessed by flow cytometry after opsonisation with mature pooled serum, autologous serum or anti‐yeast IgG. The killing capacity of the neutrophils, as indicated by the oxidative burst, was monitored by chemiluminescence. Serum IgG concentration was measured by radial immunodiffusion. In addition to clinical examination, the amount of serum amyloid A and the total leucocyte count were used as markers for infection. The phagocytic ability was impaired until age 3 weeks, when autologous serum was used as opsonin. Killing capacity was also low initially but, from 3 months onwards, chemiluminescence values were equal to or higher than in mature horses. Serum IgG decreased from 10 g/l at 2 days to 5 g/l at 2 months and then increased gradually to 10 g/l at the end of the study. These findings may in part explain the increased susceptibility to bacterial infections in young horses.

Administration of commercial Rhodococcus equi specific hyperimmune plasma results in variable amounts of IgG against pathogenic bacteria in foals

“…In this regard, IgG is the best known opsonin and acts on the initial step of pathogen clearance (Demmers and others 2001). Thus, opsonising IgGs promote R equi phagocytosis and killing in vitro (Zink and others 1985, Cauchard and others 2004).…”

Immunologic Profiles of Peripheral Blood Leukocytes and Serum Immunoglobulin G Concentrations in Perinatal Mares and Neonatal Foals (Heavy Draft Horse)

“…Newborn foals are essentially agammaglobulinemic and acquire passive immunity by ingestion and absorption of colostrum from the dam [8,9]. In the field of clinical immunology, although fragmentary information such as subpopulations of lymphocytes [10][11][12][13][14][15][16][17], responses of lymphocytes to antigens [13,[17][18][19], and phagocytic functions of neutrophils [10,11,13,15,[20][21][22][23][24][25][26][27] has been reported, sequential and comprehensive studies are rare in perinatal mares and neonatal foals. Therefore, more detailed information on immunology may enable more accurate diagnoses and may be applicable to the field of preventive medicine.…”

In vitro evaluation of complement deposition and opsonophagocytic killing of Rhodococcus equi mediated by poly‐N‐acetyl glucosamine hyperimmune plasma compared to commercial plasma products

“…The mechanism of action of antibody to PNAG is an ongoing activity in our laboratory. We did not evaluate the ability of PMNs from foals to mediate killing, and evidence exists that there are functional deficits in opsonic capacity and functional responses of neonatal foal PMNs . We do note, however, that active vaccination of pregnant mares with a PNAG conjugate vaccine as well as passive administration of PNAG‐HIP to newborn foals resulted in an aggregate protection from R. equi intrabronchial challenge of 94%, whereas 91% of foals born to control mares in the active vaccine trial or foals receiving SP in the passive protection trial developed R. equi pneumonia .…”