| Subtype | Reported biological sources | Heterodimer receptor subunits |
| A | Mast cells, macrophages, neutrophils, ILC3, ɣδ-T, NKT, CD8+, TH17 [9] | RA/RC [9] | B | Gastrointestinal tract, pancreas, gonadal tissue, chondrocytes, synovial membrane, neurons, lymphocytes [40, 60] | RA/RB [40] | C | Epithelial cells in the colon, trachea, and skin [32] | RA/RE [32] | D | Pancreas, adipose, skeletal muscle, brain, heart, lung [61] | Unidentified | E | Mast cells, macrophages, eosinophils, basophils, respiratory epithelium, and mucosa [9] | RA/RB [9] | F | Mast cells, macrophages, neutrophils, ILC3, ɣδ-T, NKT, CD8+, TH17 [9] | RA/RC [9] |
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