Antibody blocking of MHC II on human activated regulatory T cells abrogates their suppressive potential.
Natural regulatory CD4(+)CD25(+)Foxp3(+) T cells control peripheral immune responses. Freshly isolated regulatory T-cell populations are regarded as being unable to suppress the proliferation of strongly stimulated effector T cells. We now provide evidence that it is not the strength of the proliferative signal to effector T cells but activation and accessibility of regulatory T cells that determine whether suppression may occur. Human regulatory T cells were initially cocultured with allogeneic monocyte-derived dendritic cells for a short time and were then rendered accessible for effector T cells by removal of the dendritic cells. That way activated regulatory T cells effectively suppressed the proliferation of autologous effector T cells which was strongly driven by cell-sized Dynabeads coated with CD3/CD28 antibodies. Although regulatory T cells are known to display MHC II molecules and to upregulate their expression along with activation, a role of MHC II molecules in forming the contact to effector T cells was not yet envisaged. However, blocking of MHC II on activated regulatory T cells abrogated their suppressive potential. It should not be excluded that self-MHC molecules on physically accessible activated regulatory T cells arrange the contact to effector T cells.
Peiser
M
M
Institute of Molecular Biology and Bioinformatics, Charité, Berlin, Germany.
Becht
A
A
Wanner
R
R
D000906:Antibodies / Q000494:pharmacology*; D002450:Cell Communication / Q000276:immunology; D049109:Cell Proliferation; D002478:Cells, Cultured; D018920:Coculture Techniques; D003713:Dendritic Cells; D000949:Histocompatibility Antigens Class II / Q000276:immunology*; D006801:Humans; D007108:Immune Tolerance / Q000187:drug effects*; D008213:Lymphocyte Activation / Q000276:immunology; D050378:T-Lymphocytes, Regulatory / Q000187:drug effects* / Q000276:immunology
D000906:Antibodies; D000949:Histocompatibility Antigens Class II