Phenotypic and functional characterization of A20 B-cell lymphoma as an APC.

(A) Flow cytometric analysis of MHC class II, CD80 (B7.1), and CD86 (B7.2) expression on A20WT (open histogram), A20HA (hatched histogram), and splenic DCs (shaded histogram). Isotype control staining of A20WT is shown as the dashed-line histogram. (B) IL-2 production by anti-HA transgenic CD4⁺ T cells in response to cognate antigen presented by lymphoma cells or splenic DCs. The 1 × 10⁵ irradiated (10 000 rads) A20 WT (●), A20HA (▴), or splenic DCs (■) were mixed in vitro with 5 × 10⁴ highly purified naive anti-HA/I-E^dTCR transgenic T cells. Increasing concentrations of HA-peptide were added to the cultures containing either splenic DCs or A20WT. No HA-peptide was added to the A20HA–T-cell cultures. After 48 hours, supernatants were collected and assayed for IL-2 by ELISA. Values are the mean ± SE of triplicate cultures. No measurable IL-2 was produced from cultures of purified T cells pulsed with peptide in the absence of added APCs. IL-2 production by T cells cultured with A20HA alone is approximately 956 pg/mL. Shown is a representative experiment of 3 independent experiments with similar results.