Characterization of A20-specific effector cells.
(A) A20-specific reactivity of cells recovered from 2 BiV cell-vaccinated mice and restimulated twice in vitro with A20 (♦), MPC11 (▴), or medium (×). As a readout for cellular activation, the extinction obtained in the GM-CSF ELISA is shown. (B) Cytotoxicity against A20 (♦) or YAC cells (▪) exerted by effector cells that were isolated from BiV-vaccinated mice and that showed A20-specific activation after in vitro restimulation. (C) Activation of effector cells against A20 (columns 1-3) and A20Idneg cells (column 4) after stimulation with BiV protein (black column), A20 protein (white column), or A20 cells (shaded columns). Activation was measured in the GM-CSF ELISA as outlined in “Materials and methods.” The y-axis shows the ratio of the extinctions obtained with specific and control stimulation at a responder cell number of 1.25 × 105. (D) Adoptive transfer of in vitro-stimulated T cells. Spleen cells of BiV-immunized mice were stimulated only with irradiated A20 cells (▪) or with A20 cells first and BiV protein in the following stimulation rounds (♦). 5 × 105 effector cells were transferred together with a lethal A20 tumor challenge. Both CD4+ and CD8+ T cells were present in the transferred cell population. ×, tumor control.
