A comparison of foal and adult horse neutrophil function using flow cytometric techniques

Flow cytometric assays were used to compare phagocytic and oxidative burst activity of neutrophils from healthy foals less than 7 days of age with the activity of cells from healthy adult horses. The phagocytosis of Staphyloc occus aureus by foal neutrophils was less than that observed for adult neut rophils when autologous serum was used as the source of opsonins in the ass ay. The use of adult serum did not significantly improve the ability of foa l neutrophils to attach bacteria. The oxidative burst activity of foal neut rophils was equivalent to that of adult cells. However, when serum or plasm a was incorporated into the oxidative burst assay, foal neutrophils demonst rated greatly reduced autofluorescence and a suppressed response to phorbol myristate acetate (PMA), relative to that demonstrated by adult cells. The se results suggest that peripheral blood neutrophils from foals have a redu ced ability to phagocytose bacteria relative to that exhibited by adult hor se neutrophils and that the oxidative burst activity of foal neutrophils is down-regulated in response to an unidentified serum factor(s). Such change s may contribute to the increased susceptibility of foals to septic disease . (C) 2001 Harcourt Publishers Ltd.