T regulatory cells (T regs ) can activate multiple suppressive mechanisms in vitro upon activation via the T cell receptor resulting in antigen-independent suppression. However, it remains unclear whether similar pathways operate in vivo. Here, we found that antigen-specific T regs activated by dendritic cells (DCs) pulsed with two antigens suppressed T naive specific for both cognate and non-cognate antigens in vitro, but only suppressed T naive specific for cognate antigen in vivo. Antigen-specific T regs formed strong interactions with DC resulting in selective inhibition of the binding of T naive to cognate antigen, yet allowing bystander T naive access. Strong binding resulted in removal of the cognate peptide-MHCII (pMHCII) from the DC surface reducing the capacity of the DC to present antigen. The enhanced binding of T regs to DC coupled with their capacity to deplete pMHCII represents a novel pathway for T reg -mediated suppression and may be a mechanism by which T regs maintain immune homeostasis.

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A 1-cm resection margins did not increase the risk of LR. Margin width did not make a significant difference in DSS or OS. Larger resection margins increase the need for a graft or flap closure.