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Characterisation of leucocytic somatic cells in bovine milk
1Department of Veterinary Biomedical Sciences, IANR, University of Nebraska-Lincoln 68583-0905, USA.
Insights
Mammary gland milk contains T lymphocytes, a type of white blood cell crucial for immune surveillance. These cells are activated and possess memory, suggesting a role in protecting mammary tissues.
Area of Science:
- Immunology
- Cell Biology
- Mammary Gland Biology
Background:
- The mammary gland, of cutaneous origin, contains leukocytes in its stroma and milk.
- Leukocytes in milk suggest a role in local immune processes within the mammary gland.
Purpose of the Study:
- To characterize the T lymphocyte populations present in human milk.
- To investigate the potential function of milk T lymphocytes in mammary gland immunosurveillance.
Main Methods:
- Milk somatic cells were sedimented using a 43% Percoll gradient to enrich for leukocytes.
- Flow cytometry was used to identify and characterize T lymphocyte subsets based on cell surface markers (CD2, CD3, CD4, CD8, CD44, CD26, beta 1 integrin, Lam-1).
Main Results:
- T lymphocytes constituted 30-54% of leukocytes isolated from the upper Percoll gradient band.
- These milk T lymphocytes were identified as mature CD4+ or CD8+ single positive T cells.
- The cells expressed CD44, CD26, and beta 1 integrin, but lacked Lam-1, indicating an activated, memory phenotype.
Conclusions:
- Milk T lymphocytes represent a distinct, activated, memory subset.
- These cells may play a significant role in the regional immunosurveillance of mammary gland epithelia and stroma.
- Specific trafficking mechanisms likely govern the presence of these T lymphocytes within the mammary gland.
Abstract:
The mammary gland is of cutaneous origin with stromal leucocytic infiltrates and it excretes leucocytes in the milk. Milk T lymphocytes are highly enriched by sedimenting milk somatic cells in a 43 per cent preformed Percoll gradient. Thirty to 54 per cent of leucocytes, harvested from the upper Percoll band, belong to CD2+ CD3+ T lymphocytes. These milk T lymphocytes are mature CD4+, or CD8+ single positive T cells, expressing CD44, CD26, and beta 1 integrin, but not Lam-1. Milk T lymphocyte subsets may play an important role in regional immunosurveillance of the mammary epithelia and stroma. Selective mechanisms may account for the trafficking of this activated, memory T lymphocyte subset in the gland.