Naturally occurring CD4(+)CD25(+) regulatory T (nTreg) cells are essential for maintaining T cell tolerance to self Ags. We show that discrimination of human Treg from effector CD4(+)CD25(+) non-nTreg cells and their selective survival and proliferation can now be achieved using rapamycin (sirolimus). Human purified CD4(+)CD25(high) T cell subsets stimulated via TCR and CD28 or by IL-2 survived...

Naturally occurring thymocytotoxic autoantibody (NTA) was detected by cytotoxic test in the sera of very young New Zealand Black mice (within 1 month after birth); the incidence was 100% at 3 months of age. Some mice from other strains also had NTA, but at an older age and with lower incidence and antibody titer. NTA had optimal activity at 4 degrees C but was also strongly reactive at 37 degre...

In addition to naturally occurring regulatory T (nTreg) cells derived from the thymus, functionally competent Treg cells can be induced in vitro from peripheral blood lymphocytes in response to TCR stimulation with cytokine costimulation. Using these artificial stimulation conditions, both naïve as well as memory CD4(+) T cells can be converted into induced Treg (iTreg) cells, but the cellular...