Figure 3.

Antagonistic effect of Cop 1 in a split APC assay on SS-GP-25 human T cell clone specific to MBP p82–100. (A) MHC blocking. (B) TCR antagonism. Peptide 82–100 of MBP [3 μM (□) and 6 μM (○)] and Cop 1 (3–12 μM) was either coincubated on the same APC (EBV-transformed cells, 0.3 × 10⁶/ml), competing for MHC binding, or presented on different APC, which were mixed only when added to the T cells, competing on binding to the TCR. After 3 h of incubation, the EBV cells were washed and added to the T cells (1.5 × 10⁴/well). Cultures were pulsed with 1 μCi [³H]thymidine at the end of 48 h of incubation. Results are expressed as mean cpm thymidine incorporation for triplicate cultures ×10⁻³ obtained in one of two independent experiments.