Profiling calcium signals of in vitro polarized human effector CD4 + T cells

Differentiation of naive CD4+ T cells into effector subtypes with distinct cytokine profiles and physiological roles is a tightly regulated process, the imbalance of which can lead to an inadequate immune response or autoimmune disease. The crucial role of Ca2+ signals, mainly mediated by the store operated Ca2+ entry (SOCE) in shaping the immune response is well described. However, it is unclear if human effector CD4+ T cell subsets show differential Ca2+ signatures in response to different stimulation methods. Herein, we provide optimized in vitro culture conditions for polarization of human CD4+ effector T cells and characterize their SOCE following both pharmacological store depletion and direct T-cell receptor (TCR) activation. Moreover, we measured whole cell Ca2+ release activated Ca2+ currents (ICRAC) and investigated whether the observed differences correlate to the expression of CRAC genes. Our results show that Ca2+ profiles of helper CD4+ Th1, Th2 and Th17 are distinct and in part shaped by the intensity of stimulation. Regulatory T cells (Treg) are unique being the subtype with the most prominent SOCE response. Analysis of in vivo differentiated Treg unraveled the role of differential expression of ORAI2 in fine-tuning signals in Treg vs. conventional CD4+ T cells.