Single-cell observation of calcium signals in T cells and antigen-presenting cells during antigen presentation.

Intracellular calcium ion mobilization in T-cell hybridomas and antigen-presenting cells (APC) during the interaction was observed using confocal fluorescence microscopy. No calcium signal was detected in non-activated T-cell hybridomas by antigen presentation. However, in activated T-cell hybridomas, intracellular calcium ion concentration rapidly increased by antigen presentation and thereafter apoptosis was induced. On the contrary, during the interaction with T-cell hybridomas, calcium signal was induced in APCs irrespective of the activation of T-cell hybridomas. Chemical modification of APCs with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide, which is known to induce T-cell unresponsiveness during antigen presentation, inhibited cap formation of surface MHC class II molecules and suppressed calcium signals during the interaction with T-cell hybridomas.