Properties of Neutrophils Recruited into Inflammatory Foci with Homologous or Heterologous Antigen in Immunized Ewes

Studies were undertaken to determine functional properties of neutrophils attracted into involuted mammary glands of Staphylococcus aureus--immunized ewes by soluble antigens prepared from S. aureus (homologous antigen) or from Bacillus cereus (heterologous antigen). The ewes were immunized with an S. aureus vaccine known to stimulate synthesis of cytophilic IgG2 antibody, and the inflammatory responses were elicited 4-8 weeks later by infusing homologous antigen into one gland and heterologous antigen into the other. Inflammatory cells were collected at 2, 4, and 8 h postinfusion. The magnitude of the cellular responses was similar in both glands with high proportions of viable neutrophils. There were no significant differences between neutrophil populations from each gland for proportions of cells bearing cytophilic immunoglobulin, although the proportions of cytophilic immunoglobulin-positive cells from both glands were lower in 2-h exudates than in 4-h or 8-h exudates. In invitro phagocytosis assays using 3H-labeled S. aureus and B. cereus no differences could be detected between the two populations of neutrophils in terms of phagocytic efficacy using a range of bacteria-neutrophil ratios and various opsonizing treatments.