Figure 1.

SMase D suppresses SOCE in human T lymphocytes. (A) Reaction schemes for SMase D (top) and SMase C (bottom). (B) Fura-2 ratio signals of (26–54) T cells in a single 40× field, where the records show the average signals relative to the resting levels. The upper bar above the panel indicates these treatments: after 2-min rest, cells were treated with either SMase D (SMD, red) or catalytically inactive enzyme (CON, black) for 3 min, and then with 5 µg anti-CD3ε (Ab1) antibody for 2 min, and finally with 5 µg anti-IgG (Ab2) antibody for 18 min; the lower bar shows the Ca²⁺-containing solution type. (C) Peak and declining phase (at 23 min) values (error bars represent mean ± SEM; n = 5) of Fura-2 ratio signals after antibody stimulation as shown in B. (D) Fura-2 ratio signals of (17–31) T cells as in B, where the upper bar above the panel refers to these treatments: after 2-min rest, cells were treated with SMD (red) or CON (black) for 3 min and 1 µg Tg for 18 min; the lower bar shows the Ca²⁺-containing solution type. (E) Peak and declining phase (23 min) values (error bars represent mean ± SEM; n = 5) of Fura-2 ratio signals from Tg-stimulated cells for experiments as shown in D. Where present, the asterisks denote statistically significant comparisons as detailed in Materials and methods.