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Target recognition by bovine mononuclear, MHC-unrestricted cytotoxic cells
M Amadori1, I L Archetti, R Verardi
1Istituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia, Brescia, Italy.
Insights
Researchers identified a unique bovine immune cell population, distinct from B and T cells, that targets virus-infected cells. These natural killer cells recognize changes in major histocompatibility complex (MHC) class I expression on target cells.
Area of Science:
- Immunology
- Veterinary Science
- Cell Biology
Background:
- Natural killer (NK) cells are crucial for innate immunity, targeting virus-infected and tumor cells.
- Understanding bovine immune cell populations is vital for animal health and disease research.
- Previous characterization of bovine cytotoxic lymphocytes has been limited.
Purpose of the Study:
- To functionally characterize a specific population of bovine non B/non T cytotoxic lymphocytes.
- To investigate the target recognition mechanisms of these lymphocytes against virus-infected cells.
- To explore the role of major histocompatibility complex (MHC) class I antigens in this recognition process.
Main Methods:
- Flow cytometry and immuno-peroxidase staining to identify cell surface markers (CD2-, CD4-, CD8-, TcR gamma delta-, CD3+, CD45+, FcR+).
- 51Cr release assays and cell binding experiments to assess cytotoxic activity and target cell recognition.
- In vitro experiments using virus-infected bovine kidney cells as targets.
Main Results:
- Identification of a distinct bovine lymphoid killer cell population in peripheral blood leucocytes.
- Demonstration that these cells detect down-regulation or altered expression of MHC class I antigens.
- Evidence supporting the 'missing self' theory for target cell recognition, particularly in virus-infected cells.
Conclusions:
- A novel population of bovine cytotoxic lymphocytes with NK-like activity has been characterized.
- These cells play a role in recognizing virus-infected cells through altered MHC class I expression.
- Profound alterations in MHC Class I expression on virus-infected cells may be an early recognition event for the bovine immune system.
Abstract:
A population of bovine non B/non T, cytotoxic lymphocytes with natural killer activity against virus-infected and non-infected embryonic kidney cells was functionally characterized. The data obtained in experiments of flow cytometry and immuno-peroxidase staining show that a CD2-, CD4-, CD8-, TcR gamma delta-, CD3+, CD45+, FcR+ lymphoid killer cell does exist within bovine peripheral blood leucocytes. This population can detect the down-regulation of class I MHC antigens or the expression of embryonic forms thereof, as shown by experiments of 17-hour 51Cr release and binding to target cells. This model was tested in vitro in experiments on virus-infected bovine kidney cells. The emerging picture was substantially in agreement with the "missing self" theory as a possible option for target cell recognition. In this respect, the profound alteration of MHC Class I expression could represent a major early event, recognized on virus-infected cells by the immune system.