CD8⁺ T cells do not express a coreceptor for TACI. Total splenocytes from OT-1 mice were stimulated with the SIINFEKL peptide (0.1μg/mL) for 24 hours, and stained for FACS analysis with TACI-Fc followed by FITC-conjugated goat anti–human IgG. Human IgG (Ctrl IgG) was used as a control for nonspecific binding in the FACS analysis. Panel A shows the staining with TACI-Fc of unstimulated and peptide-stimulated CD8⁺ T cells; panel B shows CD69 expression in unstimulated and peptide-stimulated CD8⁺ T cells. Substantial binding of TACI-Fc to either unstimulated (A, filled histogram) or peptide-stimulated (A, empty histogram) CD8⁺ T cells was not detectable. The staining with TACI-Fc is in fact highly comparable with the Ctrl IgG control in both cell preparations. T-cell activation has been proven by the selective CD69 expression in the peptide-stimulated T cells (B, light gray histogram).