Figure 10. CD25^lowFoxp3⁺ Tregs suppress high avidity T cells and traffic preferentially to the tumor.

(A) CD25^low and CD25^high CD4⁺ Treg cells suppress high avidity T cell activation in vitro. CD25^low or CD25^high CD4⁺ FoxP3^gfp+, DC, and CFSE-labeled high avidity Thy1.2⁺ CD8⁺ neu-specific T cells were mixed as described in the Methods. CFSE dilution was measured on days 3 and 5. CD4⁺ T cells from FVB/N mice were used as controls. High+DCs = High avidity T cells+DCs. High+DCs+CD4s = High avidity T cells+DCs+FVB/N CD4⁺ T cells, (B) CD25^lowCD4⁺FoxP3⁺ Tregs trend toward suppression in vivo. neu-N/FoxP3^gfp mice were given tumor and vaccinated as in the Methods. CD4⁺CD25^low Tregs were isolated 1 week later and transferred to FVB/N-TgN(TIE2GFP)287Sato mice which were then vaccinated. CD8⁺ T cells were isolated 2 weeks later and tested for the ability to secrete IFNγ in response to RNEU_420–429. Data are presented as % RNEU_420–429-specific, IFNγ⁺ of CD8⁺ T cells. This experiment was done twice with similar results. (C) CD25^low Tregs traffic preferentially to the tumor. neu-N mice received tumor and one week later received Cy, vaccine, 6×10⁶ high avidity T cells, and 5×10⁵ CD25^low or CD25^high CD4⁺GFP⁺ Tregs. On day 5 CD25^low or CD25^high CD4⁺GFP⁺ Tregs recovered from tumors, spleens, TDNs, and VDNs were enumerated as a fraction of the total # of FoxP3⁺ T cells at each site (n = 3mice/group). * = p<0.05. This experiment was repeated three times with similar results.