TCR down-regulation in cells expressing 1 or 2 Vα chains. The mean fluorescence intensity of TCR Vα expression was measured before and after incubation for 1 hour with an anti-Vα2 mAb. The results are shown as the relative decrease in fluorescence as compared with the original intensity (indicated by the dotted line; Vα2 on Vα2⁺Vα12^– cells: □;Vα2 on Vα2⁺Vα12⁺ cells: ▦;Vα12 on Vα2^– Vα12⁺ cells: ▪). The asterisks above the error bars indicate the statistical significance of the change in fluorescence (ns indicates not significant, **P < .005); the comparison between single- and dual-specific Vα2⁺ cells is also shown. There was no statistically significant difference between CD25^hi and other CD4⁺ cells (n = 6).