FUNCTIONAL VARIATION IN ENDOGENOUS AND EXOGENOUS IMMUNOGLOBULIN BINDING TO BOVINE NEUTROPHILS RELATIVE TO PARTURITION

Ten healthy first- and second-lactation Holstein cows were observed fr om 1 week before to 1 week after calving and at postpartum day 30 to d etermine polymorphonuclear neutrophil (PMN) functional variation and i mmunoglobulin binding profiles. Blood and mammary PMN were obtained 3 times weekly and within 24 hours of calving. Functional traits measure d included phagocytosis of Staphylococcus aureus and in vitro chemotax is through micropore filters in a Boyden chamber. Additionally, PMN we re evaluated for endogenous binding of IgG1, IgG2, IgA, and IgM before and after in vitro chemotaxis. Exogenous binding of the same isotypes was determined after incubation in pooled colostrum, purified immunog lobulin, and pooled sera. Phagocytosis results indicated a significant and transient increase in percentage of milk PMN with associated, rat her than phagocytosed, bacteria for 1 week after calving. Blood PMN ph agocytosis was not significantly different during this period. Though total chemotaxis was essentially unchanged, the percentage of PMN that were unable to complete migration increased substantially on the day of calving, an effect that disappeared by postpartum day 4. A signific ant (P < 0.01) positive correlation (r = 0.29) between percentage of P MN migrating completely through the micropore filter and percentage of blood PMN with associated bacteria was observed. Changes were not obs erved in endogenous immunoglobulin binding, with the exception of a pe ak in relative fluorescence intensity for IgG, on the day of calving; this disappeared within 2 days after calving. Correlations between rel ative intensities of IgG2 and IgM, and percentage of mammary neutrophi ls phagocytosing were 0.37 and 0.70. Exogenous binding of antibody to blood neutrophils before chemotaxis was generally accomplished most ef fectively by pooled colostrum, whereas use of pooled sera markedly red uced binding and percentage and intensity of IgM in all cases. Binding of all isotypes was slightly higher before than after calving. Incuba tion of blood neutrophils in isotypes G1, G2, A, and M after chemotaxi s yielded lower immunoglobulin binding among all isotypes, particularl y IgM. Fluctuations in neutrophil function were observed immediately a round parturition, and these changes correlated strongly with endogeno us immunoglobulin-binding profiles.