Macrophages in bovine milk

Area of Science:

• Veterinary immunology
• Cell biology
• Bovine mammary gland physiology

Background:

• Mammary gland secretions contain various cell types.
• Mononuclear cells in bovine milk are often misidentified.
• Understanding these cells' function is crucial for mammary health.

Purpose of the Study:

• To characterize the functional properties of vacuolated mononuclear cells in normal bovine milk.
• To determine if these cells possess macrophage-like characteristics.
• To clarify the identity of these commonly observed milk cells.

Main Methods:

• In vitro assays assessing neutral red uptake, adherence, and spreading on glass.
• In vitro phagocytosis assays using live Streptococcus agalactiae and Staphylococcus aureus.
• In vivo assessment of neutral red uptake and phagocytosis of formalin-killed Staphylococcus aureus.

Main Results:

• Vacuolated mononuclear cells concentrated neutral red in vitro and in vivo.
• These cells adhered rapidly and spread on glass surfaces.
• Phagocytosis of both live and killed bacteria (Streptococcus agalactiae and Staphylococcus aureus) was observed.

Conclusions:

• The studied vacuolated mononuclear cells exhibit key functional properties of macrophages.
• These findings suggest a reclassification of these cells from epithelial cells to macrophages.
• This identification has implications for understanding bovine mammary gland immunity and health.