Table 2.
Innate lymphoid cells characteristics.
| Characteristic | ILC group 1 | ILC group 2 | ILC group 3 |
|---|---|---|---|
| Cell type | NK cells (CD56dim/bright NKp46+) | IL1R+ | ILC3 and LTi cells |
| ILC1 cells not cytotoxic | IL23R+ | Some CD56+ cells | |
| Main cytokine produced | IFNγ | IL5 and IL13 triggered through IL25 or IL33 | IL22 and/or IL17 |
| IFNγ | |||
| Cytolytic activity | Yes (NK cells) | ||
| Main transcription factor expressed | T-bet | RORα | RORγt |
| Eomes | GATA3 | ||
| Peculiar phenotypic features | c-kit− (CD117) | c-kit− | c-kit+ |
| IL12Rβ2+ | IL12Rβ2− | IL12Rβ2− | |
| Subunits of IL25R and IL33R | |||
| Common phenotypic features | IL7Rα+ (CD127) | IL7Rα+ | IL7Rα+ |
| NKRP1a+ (CD161) | NKPRP1a+ | NKRP1a+ | |
| Immune function | Viral infections, tumor surveillance | Tissue defense/homeostasis | Inflammation (IL17+IFNγ+ colitis) |
| NK IFNγ Inflammation (ILC1) | Protection (Citrobacter rodendrium ILC3 IL22+) | ||
| Gut barrier, wound healing, and epithelial proliferation | |||
| Lymph node formation (IL17+) | |||
| Main tissue localization | Lymphoid organs, uterus, lung, gut, liver | Lung, adipose tissue, gut | Gut lamina propria and cryptopatches, mesenteric lymph nodes, palatin tonsil |
| Role in autoreactivity | IBD (CD56bright NK cells) | Murine models of gut parasitic infections | Murine models of colitis |
| Human IBD | Chron disease |
Innate lymphoid cells (ILCs) are mucosa associated lymphoid cells which can express some markers of NK cells. It has been proposed to include NK cells within the ILC1 subset of ILC. NK cells are CD56+ and display strong cytolytic activity while ILC produce a set of different cytokines depending on the subset they belong to. This dichotomy is not so well defined as some ILC3 cells can express CD56 and thus it is still debate whether NK and some ILC subsets may be inter-converted due to intrinsic plasticity. IBD, inflammatory bowel disease.