Restimulation of suppressor lines reveals cytokine production defects and cell surface LAP expression. Levels of cytokine produced in supernatants 48 hours after restimulation. (A) Cell lines were reactivated with anti-CD3/CD28 beads. (B) Cells were reactivated with PMA/ionomycin. Control CD25^--derived cell lines are indicated by blue bars and CD25⁺-derived cell lines by burgundy bars. Cell surface activation antigen expression 24 hours after restimulation with anti-CD3/CD28 beads. (C) Expression of CD69, OX40 (CD134), and GITR is intact. (D) Cell surface LAP expression is specific for CD25⁺-derived cell lines. Resting cell lines are indicated by blue lines and restimulated cell lines by red lines. Resting cell lines were negative for these activation antigens prior to restimulation.