Interleukin-21 (IL21) is a 162-residue protein from Homo sapiens. This is its AlphaFold structure prediction, created 1 Aug 2025. UniProt accession: Q9HBE4.
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The mean pLDDT of this model is 83.4 (confident overall). pLDDT is AlphaFold's per-residue confidence score from 0 to 100. In MolViewer, choose the B-factor color scheme to color the model by pLDDT, because AlphaFold stores it in the B-factor column.
| pLDDT band | Meaning | Share of residues |
|---|---|---|
| Above 90 | Very high: backbone and side chains are usually accurate | 56% |
| 70 to 90 | Confident: backbone generally right | 20% |
| 50 to 70 | Low: treat with caution | 19% |
| Below 50 | Very low: often disordered regions | 5% |
What pLDDT means and how to read it
Cytokine with immunoregulatory activity. May promote the transition between innate and adaptive immunity. Induces the production of IgG(1) and IgG(3) in B-cells (By similarity). Implicated in the generation and maintenance of T follicular helper (Tfh) cells and the formation of germinal-centers. Together with IL6, control the early generation of Tfh cells and are critical for an effective antibody response to acute viral infection (By similarity). May play a role in proliferation and maturation of natural killer (NK) cells in synergy with IL15. May regulate proliferation of mature B- and T-cells in response to activating stimuli. In synergy with IL15 and IL18 stimulates interferon gamma…
Secreted
Compare the prediction with experimentally determined structures of the same protein:
| PDB ID | Method | Resolution | Chains and residues |
|---|---|---|---|
| 3TGX | X-ray | 2.8 Å | B/D/F/H/J/L/N/P=30-162 |
| 8ENT | X-ray | 2.83 Å | A/D/G/J=30-162 |
| 2OQP | NMR | A=30-162 |
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