Effects of bovine colostrum, foal serum immunoglobulin concentration and intravenous plasma transfusion on chemiluminescence response of foal neutrophils

Summary. The effects of bovine colostrum, absorption of equine colostral immunoglobulins and age on phagocytic and serum opsonizing activity of nine clinically healthy foals were examined. Cells and serum were collected prior to suckling and at 7, 14 and 28 days of age. Seven foals had serum IgG concentrations >600mg/dl whereas two foals had <350mg of IgG/dl. Phagocytic and serum opsonic activity of eight clinically ill foals with <400mg of IgG/dl of serum were also examined before and after plasma transfusion. Phagocytic and serum opsonizing activities were evaluated by an assay for chemiluminescence (CL) after addition of opsonized streptococci. Results showed that bovine colostrum stimulated CL of foal neutrophils. Preliminary characterization of opsonins in bovine colostrum by ammonium sulphate fractionating and heat inactivation indicated that opsonins generating CL were mainly associated with immunoglobulin G. Chemiluminescence generated by foal neutrophils varied with age with foal neutrophils collected at day 14 producing more CL than adult neutrophils ( P <0.05). Foal serum opsonizing activity was similar to adult opsonizing activity if serum IgG concentrations were >600mg/dl but it was less if IgG concentration was <350mg/dl ( P <0.05). Chemiluminescence generated by foal and adult neutrophils was higher when post-transfusion foal serum was used as the source of opsonin than when pre-transfusion foal serum was used ( P <0.05). When adult serum was the opsonin, chemiluminescence of foal neutrophils collected before and after plasma transfusion did not differ. The increase in CL following plasma transfusion was probably due to an increase in serum opsonizing activity.