Alloantigen-specific suppressor activity of anergic T cells.

Anergic T cells were found to display alloantigen-specific suppressor activity. First, 1 × 10⁵ anergic CD4⁺ (panel A) or CD8⁺ (panel B) T cells (ATs) (generated by stimulation with IL-10–treated DCs) were cocultured with an equivalent number of activated control T cells (CTs) (stimulated with mature DCs) and restimulated with mature DCs (2 × 10⁴) from the same DC donor used during induction of anergy (hatched bars) as described in “Materials and methods.” A coculture of the same number of T cells (2 × 10⁵) (CTs) with mature DCs served as controls (black bars). To test the alloantigen specificity, anergic T cells were cocultured with T cells from a second unrelated donor in a second experiment. Anergic T cells (1 × 10⁵) (ATs) stimulated with allogeneic DCs (1 × 10⁴) and allogeneic and syngeneic activated control T cells (1 × 10⁵) (syn CTs, allo CTs) activated by allogeneic DCs (1 × 10⁴) from the same donor used in the primary culture served as controls (dotted bars). T-cell proliferation was measured after 3 days of incubation and an additional 16-hour pulse with ³H-Tdr (37 kBq per well) by means of a liquid scintillation counter. Similar results were observed in 5 independent experiments.