CD137 is a receptor expressed on the surface of activated CD4 and CD8 T cells, (FOXP3pos) T regulatory cells, dendritic cells, monocytes, eosinophils, natural killer cells and natural killer T cells. It has been widely used as a surrogate marker for antigen-specific T cells and purification of antigen-specific T cells after in vitro antigen stimulation in mice and humans. So far, there are no anti-CD137 antibodies commercially available for pigs or any other veterinary species. Researchers at Virginia Tech have created a monoclonal antibody that specifically detected porcine CD137 in immunofluorescence and flow cytometry assays.
Anti-CD137 antibodies may be useful for veterinary research and diagnostic laboratories for the following purposes:
(1) Characterization of antigen-specific CDS and CD4 T cells in response to in vitro antigen stimulation of peripheral blood mononuclear cells. So far, veterinary research laboratories depend on IFN-y ELISPOT and intracellular IFN-y FACS staining for the characterization of antigen-specific T cells in response to in vitro antigen stimulation of peripheral blood mononuclear cells. CD137 expression on resting cells is absent and it is up-regulated only in response to antigen stimulation. Staining of antigen stimulated T cells with anti-CD137 antibodies provides specific detection that is potentially superior than IFN-gamma staining.
(2) Using anti-CD137 antibodies, in vitro antigen-stimulated or in vivo antigen-specific T cells can be isolated as live cells using flow cytometry cell sorting or magnetic cell sorting. In mouse or human studies, it has been shown that anti-CD137 antibodies are superior in purification of antigenspecific T cells from naive repertoire or memory T cells after in vitro antigen stimulation when compared to other activation markers such as CD25, CD69, etc. The purified cells can be further cultured for establishing T cell lines and in vitro epitope screening.
(3) CD137 is a novel diagnostic marker of a selected group of hemato-lymphoid tumors including classical Hodgkin lymphoma, T cell and NK/T cell lymphomas and follicular dendritic cell neoplasms. It may be useful for identification of aforementioned tumor biopsy samples of dogs and cats through immunohistochemistry staining.