Figure 5. Optical control of intracellular Ca²⁺ signal in CD8⁺ T cells overcomes immunosuppression.

(a) 2 × 10⁵ B16F10 cells in 10 μl PBS were intradermally injected into the ear and flank. Expression of CD107a on Pmel-1 CD8⁺ T cells in B16 tumours in the ear with (optical LED+light) or without (optical LED+dark) light stimulation of tumours in the ear (light, n=5; dark, n=5). (b) Size of B16 tumours both in the ear and flank treated with adoptive transfer of CatCh-expressing Pmel-1 CD8⁺ T cells with (optical LED+light) or without (optical LED+dark) light stimulation of the ear (light, n=5; dark, n=5). (c) Expression of CD69 on OT-I CD8⁺ T cells after re-stimulation with N4 peptide (1 μg ml⁻¹) loaded irradiated splenocytes in the absence or presence of CGS21680 (10 μM, n=4). (d) Expression of CD69 on OT-I CD8⁺ T cells after re-stimulation with N4 peptide (1 μg ml⁻¹) loaded irradiated splenocytes in the absence or presence of PGE₂ (5 μM, n=4). (e) OT-I CD8⁺ T cells were incubated with PBS or sFasL (100 ng ml⁻¹) for 16 h. Apoptotic OT-I CD8⁺ T cells were stained for Annexin V (n=4). (f) Killing of N4 peptide-loaded EL-4 cells after light stimulation of CatCh- or GFP-expressing OT-I CD8⁺ T cells in the absence or presence of MDSC (1:1) (n=6).