Figure 6. Sp1 prevents CD8⁺CD28⁻ T lymphocytes from apoptosis.

A. CD8⁺ T cells from C57BL/6 spleens were treated in medium in the absence or presence of staurosporine with Sp1, mSp1 (100 µg/ml, respectively), or without antigen for 12 h. Magnetically separated CD8⁺CD28⁻ and CD8⁺CD28⁺ cells were stained with FITC-conjugated Annexin V and 5 µl propidium iodide (PI), and prepared for flow cytometry. One representative result out of three stainings with cells from 3 mice, respectively, is displayed. The numbers in the quadrants of the dot plots represent the percentage ±SD (n = 3) of cells stained positive for the respective markers. B. Sp1 inhibits staurosporine-induced caspase 3 activity in CD8⁺CD28⁻ T cells. CD8⁺, CD8⁺CD28⁻, and CD8⁺CD28⁺ T cells were treated for 4 h with mSp1, mSp1 (100 µg/ml, respectively), or in medium alone. SDS-PAGE of the whole cell extract was performed. One representative out of four western blots performed with a caspase 3- and a β-actin-specific antibody as a control is shown.