GITR triggering does not abrogate regulatory T cell function.

<p>(A) <i>In vitro</i> suppressive capacities of CD4⁺CD25⁺ T cells recovered from anti-GITR antibody-treated NOD mice. CD4⁺CD25⁻ and CD4⁺CD25⁺ T cells were recovered from the spleen cell of 6-week-old NOD mice injected with anti-GITR antibody (0.8 mg on day 10, 17 and 24) or of control mice. Criss-cross co-cultures were performed by incubating the CD4⁺CD25⁺ T cells from anti-GITR-treated NOD mice with CD4⁺CD25⁻ T cells from control animals and inversely. The two T cell subsets (CD25⁺ and CD25⁻) were cultured at a 1/1 ratio in presence of APCs and CD3 antibody for 72 hrs. Data represent the mean of 4 experiments. (B) FoxP3 expression by CD4⁺CD25⁺ T cells recovered from the spleen of 5-week-old NOD mice treated with anti-GITR antibody. (C) CD4⁺CD25⁺ T cells from unmanipulated NOD mouse spleen were stimulated with coated CD3 antibody (0.5 µg/ml) in the presence of increasing concentrations of anti-GITR antibody ranging from 0.08 to 50 µg/ml. (D) CD4⁺CD25⁺ T cells were recovered from 6-week-old NOD mice and cultured with CD3 antibody (0.5 µg/ml) or CD3+GITR antibodies (50 µg/ml) for 48 hrs. Cells were harvested, washed and their suppressive capacity was evaluated after 72 hrs incubation with freshly isolated CD4⁺CD25⁻ T cells. Freshly isolated CD4⁺CD25⁺ T cells were used as controls. The results shown here are representative of at least three experiments.