Monoclonal antibodies raised to the human FOXP3 protein can be used effectively for detecting Foxp3(+) T cells in other mammalian species.

A population of primarily CD4(+)CD25(+) regulatory T cells (Tregs), that have a critical role in maintaining the balance between tolerance and immunity, have been identified through their ability to provide protection against autoimmune disease. There is considerable interest in further exploring the role that Tregs play in autoimmune disease, cancer, and in regulating the immune response to pathogens. Currently the best single marker for labelling Tregs is the forkhead transcription factor FOXP3. Consistent with its essential functional role, sequence alignment showed that the FOXP3 protein is highly conserved across mammalian species. Lymphoid tissues were analysed for nuclear Foxp3 protein expression by immunohistochemistry to evaluate the utility of monoclonal antibodies raised to the human FOXP3 protein for labelling Foxp3(+) Tregs in other mammalian species. The T-cell specificity of those anti-FOXP3 antibodies that gave the most effective staining on each species was confirmed by double labelling with FOXP3 and CD3. Antibodies 236A/E7 and 206D/B1 showed least reactivity with other species, while 259D/C7 commonly exhibited non-specific nuclear staining of non-human lymphoid tissues. Antibodies 86D/D6, 150D/E4 and 157B/F4 are recommended as those which are most effective for labelling Foxp3(+) Tregs in studies utilising animal models.