FIG. 3.

Intermediate- but not high-avidity TCR-CD4 ligands induce maximal Elk-1 transactivation and IL-2 responses in CD45RO⁺ T cells. CD45ABC⁺ and CD45RO⁺ BW cells were transfected with the Elk-1–GAL4–5×GAL4–luciferase construct (A and C) or with the IL-2–luciferase construct (B and D). At 24 h posttransfection, 10⁵-cell aliquots were incubated in 96-well plates precoated with MAb 3D3 or 5A. After stimulation, cells were collected and lysed and the luciferase activity was measured and normalized against the protein concentration. (A and B) Transcriptional functional assay monitoring activity of Elk-1 (A) or the IL-2 minimal promoter (B) in CD45RO⁺ 19.9 cells stimulated with increasing concentrations of anti-TCR clonotypic MAb 3D3 (open) or 5A (closed). (C) Comparison of maximal Elk-1 activations during stimulation with MAbs 3D3 (3D3^max) and 5A (5A^max) in three independent CD45ABC⁺ clones (17.11, 17.4, and 23.3) clones, two CD45RO⁺ clones, (19.9 and 18.16), and one CD45 Exon-1 BW clone. (D) Similar analysis of the maximal responses from the IL-2 promoter conducted with one representative CD45ABC⁺ clone and one CD45RO⁺ clone. The data in panel D are the ratios between the maximal responses obtained with the two antibodies for each cell clone. The data shown are representative of two to five independent experiments. Ab, antibody.