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Updated: Aug 15, 2026
Subcutaneous Infection of Methicillin Resistant Staphylococcus Aureus (MRSA)
Published on: February 9, 2011
Migration of polymorphonuclear leukocytes into the bovine mammary gland during experimentally induced Staphylococcus
Abstract:
The process of neutrophilic polymorphonuclear leukocyte (PMN) migration in the bovine mammary gland during experimental Staphylococcus aureus challenge was studied using light and electron microscopies. The PMN were observed in various stages of margination in capillary lumens and migration into perivascular spaces. In infected tissue showing little evidence of epithelial damage, numerous PMN were accumulated in the perivascular space and aligned against the epithelial basal lamina, but not in the alveolar lumen. Other areas of infected tissue showed progressive tissue degeneration (autophagic vacuoles, vesiculation of endoplasmic reticulum, and cellular debris in the luminal milk) with the appearance of numerous PMN in lumens. The PMN were observed between the basal end of adjacent epithelial cells having intact tight junctions, but were never seen traversing the junctional complex. Some PMN lying between intact epithelial cells appeared to have ingested fat globules before entering the lumen. Although the mechanism by which PMN crossed tight junctions was not explained, alveoli with a portion of the epithelium sloughed off were frequently seen. The PMN appeared to be entering alveoli in large numbers at these damaged sites. There was also marked PMN infiltration in tissue from teat and gland cisterns of S aureus-infected quarters.
Insights
Neutrophil migration into bovine mammary glands during Staphylococcus aureus infection involves movement into perivascular spaces and lumens. PMN infiltration primarily occurs through damaged epithelial sites, not intact tight junctions.
Area of Science:
- Veterinary Pathology
- Immunology
- Bovine Mastitis Research
Background:
- Bovine mastitis, often caused by Staphylococcus aureus, involves significant inflammatory responses.
- Neutrophilic polymorphonuclear leukocytes (PMN) are critical immune cells in combating bacterial infections in the mammary gland.
Purpose of the Study:
- To elucidate the migration pathways of PMN within the bovine mammary gland during experimental Staphylococcus aureus challenge.
- To investigate the cellular mechanisms and tissue interactions during PMN infiltration.
Main Methods:
- Light and electron microscopy were employed to visualize PMN behavior and tissue changes.
- Experimental Staphylococcus aureus challenge model in bovine mammary glands.
Main Results:
- PMN margination and migration into perivascular spaces were observed.
- In early stages, PMN accumulated in perivascular spaces without entering alveolar lumens; later, tissue degeneration correlated with PMN presence in lumens.
- PMN were seen between epithelial cells but not traversing intact tight junctions; sloughed epithelium facilitated PMN entry into alveoli.
Conclusions:
- PMN migration into infected bovine mammary glands is complex, occurring via perivascular spaces and alveolar lumens.
- Epithelial damage, particularly sloughing, appears to be the primary route for PMN entry into alveolar lumens.
- Understanding these pathways is crucial for managing bovine mastitis.
