P2X1 and P2X4 receptors regulate Ca²⁺ signaling in response to TCR stimulation. Effects of silencing P2X receptors in Jurkat cells (A) or pharmacologic P2X receptor inhibition of human primary CD4⁺ T cells (PBMCs; B) on Ca²⁺ signaling. Cells were stimulated by TCR activation (0.5 μg/mL anti-CD3 antibody). The response was assessed by flow cytometry using Fluo-3 as a Ca²⁺ indicator. Triple silencing was carried out using one-third of siRNA per gene compared with silencing of individual genes. Graphs depict representative results from at least 3 experiments performed with cells from different donors.