title: Large-scale expansion of rat CD4+ CD25+ T(reg) cells in the absence of T-cell receptor stimulation.
abstract: T-cell receptor (TCR) stimulation is both central to homeostatic maintenance of CD4(+) CD25(+) regulatory T cells (T(reg) cells) in vivo and a prerequisite for the initiation of suppression by T(reg) cells, both in vivo and in vitro. However, TCR-independent stimulation of T(reg) cells, e.g. with superagonistic CD28-specific monoclonal antibodies (CD28-SA), not only expands these cells in vivo but, as we show here, also mediates large-scale expansion of rat T(reg) cells in vitro. Interestingly, CD28-SA stimulation plus interleukin (IL)-2 was even superior to conventional costimulation plus IL-2 in promoting T(reg) cell growth in vitro. Despite their highly activated phenotype suppression by T(reg) cells expanded in the absence of TCR stimulation remained fully dependent on TCR-triggering for initiation and cell contact was required to exert suppression. With regard to the regulation of suppression by CD28 stimulation we observed that neither the presence of a conventional anti-CD28 monoclonal antibody nor a CD28-SA generally rendered conventional T cells resistant to suppression by preactivated T(reg) cells. Taken together, we provide a novel protocol for long-term propagation of T(reg) cells in vitro and our data are the first to reveal a difference in the signals required for activation and expansion of T(reg) cells and those, involving the TCR, necessary for the initiation of suppression.
authors.affiliation: University of Würzburg, Institute for Virology and Immunobiology, Würzburg, Germany.
authors.forename: Niklas
authors.initials: N
authors.lastname: Beyersdorf
authors.forename: Karen
authors.initials: K
authors.lastname: Balbach
authors.forename: Thomas
authors.initials: T
authors.lastname: Hünig
authors.forename: Thomas
authors.initials: T
authors.lastname: Kerkau
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D018106:CD28 Antigens / Q000032:analysis; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D049109:Cell Proliferation; D002478:Cells, Cultured; D018920:Coculture Techniques; D007108:Immune Tolerance; D007376:Interleukin-2 / Q000276:immunology; D053645:Interleukin-2 Receptor alpha Subunit / Q000032:analysis*; D008213:Lymphocyte Activation / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D051381:Rats; D011917:Rats, Inbred Lew; D011948:Receptors, Antigen, T-Cell / Q000276:immunology*; D016176:T-Lymphocyte Subsets / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D018106:CD28 Antigens; D007376:Interleukin-2; D053645:Interleukin-2 Receptor alpha Subunit; D011948:Receptors, Antigen, T-Cell