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Published on: July 11, 2015
Study of T-lymphocyte subsets of healthy and Mycobacterium avium subsp. paratuberculosis-infected cattle
1Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin, Madison 53706, USA.
Insights
In cattle with paratuberculosis, CD4+ T-lymphocytes are the main producers of gamma interferon (IFN-γ). Other T-cell subsets contribute less to this specific immune response, suggesting limited roles for IFN-γ in gammadelta+ T-cell function.
Area of Science:
- Immunology
- Veterinary Medicine
- Cell Biology
Background:
- Mycobacterium avium subsp. paratuberculosis (MAP) causes Johne's disease in cattle.
- Understanding T-lymphocyte subset roles in host defense is crucial for developing effective control strategies.
- Previous studies in other species indicate varying contributions of T-cell subsets to immune responses.
Purpose of the Study:
- To determine the relative contributions of different T-lymphocyte subsets (CD4+, CD8+, gammadelta+) to host defense in cattle infected with MAP.
- To quantify lymphoproliferation and gamma interferon (IFN-γ) production by these subsets in response to specific antigens and mitogens.
Main Methods:
- Purification of T-lymphocyte subsets using monoclonal antibodies and magnetic bead separation.
- Verification of cell purity using flow cytometry.
- Measurement of lymphoproliferation and IFN-γ production via enzyme-linked immunosorbent assay (ELISA) in response to phytohemagglutinin (PHA) and an MAP antigen preparation (A-PPD).
Main Results:
- CD4+ lymphocytes were the primary producers of IFN-γ in response to PHA, followed by CD8+ cells; gammadelta+ T cells produced minimal IFN-γ.
- A significant correlation was observed between proliferation and IFN-γ production in response to A-PPD, but not PHA.
- Peripheral blood mononuclear cells (PBMC) showed higher IFN-γ production than CD4+ T cells in response to A-PPD.
Conclusions:
- CD4+ T-lymphocytes are the major source of IFN-γ in cattle, similar to other animal species.
- The role of gammadelta+ T cells in paratuberculosis is unlikely to be mediated through significant IFN-γ production.
- These findings highlight the importance of CD4+ T-cell responses in cattle immunity against MAP infection.
Abstract:
The relative contributions of T-lymphocyte subsets to host defense in cattle infected with Mycobacterium avium subsp. paratuberculosis is reported. The subsets were purified with appropriate monoclonal antibodies and a magnetic bead column separation system, and their purity was verified by flow cytometry. Biological activity of each subset, expressed as lymphoproliferation and gamma interferon (IFN-gamma) production, was measured in response to phytohemagglutinin (PHA) and an M. avium antigen preparation (A-PPD). IFN-gamma was measured by antibody capture enzyme-linked immunosorbent assay. The results showed a correlation between proliferation and IFN-gamma production in response to A-PPD but not to PHA. In response to PHA, CD4+ lymphocytes were the most prolific producers of IFN-gamma. CD8+ lymphocytes produced IFN-gamma to a lesser extent, whereas gammadelta+ T lymphocytes produced little or no IFN-gamma. Differences observed between the amount of IFN-gamma produced by CD4+ versus CD8+ cells and CD4+ versus gammadelta+ cells were significant (P < 0.01), but those between peripheral blood mononuclear cells (PBMC) and CD4+ T cells were not. Similar responses to A-PPD were observed except that PBMC produced higher levels of IFN-gamma than did CD4+ T cells. These data for cattle are similar to observations made for other animal species, where CD4+ cells are the major type of T lymphocytes producing IFN-gamma. They further suggest that whatever the role gammadelta+ T cells may play in paratuberculosis, it is not likely to be mediated by IFN-gamma production.
