Table 1.
The ABC of CD4+CD28null T-cell biology
| CD4+CD28null T cells | CD4+CD28+ helper T cells | Ref. | |
|---|---|---|---|
| CD28 co-stimulatory receptor | Absent | Present | 3 |
| OX40/4-1BB co-stimulatory receptors | Up-regulated | Absent1 | 1 |
| T-cell receptors (TCR) | Oligoclonal | Polyclonal | 8,9 |
| Activating natural killer cell receptors (e.g. NKG2D) | Present | Absent | 14 |
| CX3CR1 (fractalkine receptor) | Present | Absent | 36 |
| ‘Signature’ cytokines | interferon-γ, tumour necrosis factor-α | Variable2 | 1,11 |
| Cytolytic enzymes (perforin, granzymes) | Present | Absent | 1,12 |
| Cytotoxic function | Present | Absent | 1,13 |
| Resistance to apoptosis induction | Yes | No | 2,58 |
| Ability to provide help signals to B cells | No | Yes | 11 |
| Sensitivity to suppression by regulatory T cells | Decreased | Yes | 15 |
1
OX40 and 4-1BB expression are induced only after T-cell activation.
2
Depending on the T helper (Th) cell subset (e.g. interferon-γ for Th1; interleukin-4 for Th2; interleukin-17 for Th17, etc.).