Table 37.
Summary of key functional and phenotypic human Treg markers
| Marker | Technical notes* | References |
|---|---|---|
| Functional and/or phenotypic makers of human Tregs | ||
| IL-10 | Difficult to detect in peripheral Tregs. PMA/Ionomycin stimulation for at least 6 hours is required; staining with the IL- 10 capture assay (Miltenyi Biotech) or other stimuli may give better results. Recommended clone is JES3-9D7. | [409-411] |
| LAP and GARP | Expression is optimal after 24 hours of TCR stimulation. | [412, 413] |
| LAG-3 | Low expression on non-activated Tregs. Recommended clone for activated cells is REA351. Also described as a marker of type 1 regulatory T cells. | [410, 414, 415] |
| PD-1 | Levels are increased after activation or with intracellular staining. | [416] |
| AREG | Expression is optimal after PMA/Ionomycin stimulation for 4 hours. Works with FOXP3 buffers. Recommended Ab clone is BAF262 (R&D systems). | [408] |
| CD39 | A common single nucleotide polymorphism (SNP) in humans results in low CD39 expression. Individuals who are homozygous for this SNP have <10% CD39+ Tregs compared to ~ 50% CD39+ in heterozygotes or non-carriers. Clone A1 does not block CD39 enzymatic function. | [417-419] |
| HLA-DR | Not expressed on murine Tregs; defines a memory and highly suppressive population. | [420] |
| CTLA-4 (CD152) | Due to rapid receptor internalization, staining is improved with intracellular staining or inclusion of the mAb for a period of time in culture. | [421, 422] |
| Blimp-1 | Expression is increased after activation. Recommended clone is 6D3. | [423] |
| CD49d | In combination with CD127, low level expression of CD49d can be used to differentiate between activated Tconv and Treg. | [424] |
| Ki67 | Marker of cell proliferation. Although anergic in vitro, when tested directly ex vivo, Tregs show a high proportion of cells expressing Ki67. | [425] |
| CCR8 | Expressed on FOXP3+BATF+CCR8+ Treg cells in peripheral human tissues such as fat, liver or skin. | [378] |
| Not known to be detectable on human peripheral blood Tregs | ||
| CD73 | Despite being expressed on murine Tregs, low/no expression of these markers has been observed on non-activated, peripheral human Tregs in healthy individuals. More research is needed to assess if these proteins may be expressed on tissue-infiltrating Tregs, and/or in various disease/cell activation states | [426, 427] |
| CD103 | [360, 428] | |
| ST2 (IL33R) | [387, 408] | |
| Neuropilin-1 | [369, 429] | |
| OX40 | [430, 431] | |
*
Technical notes are from our experience and largely unpublished.