A, Overall tyrosine phosphorylation induced by pMHC tetramers. B and C, Mobilization of intracellular calcium in response to peptide-pulsed (1 μM) DCs (in B, using Indo-I-Am) or pMHC tetramers (1 μg/ml) (in C, using Fluo-3-AM). Data in C correspond to gated tetramer+ cells. D, Erk1/2 activation 10 minutes after stimulation with peptide-pulsed DCs. Western blots were probed with phospho-Erk1/2- or β-actin-specific antibodies. The densitometric values (normalized to β-actin) for NRP-A7, NAT-32 and NRP-E6 as compared to TUM were 14, 12 and 13-fold (naïve T-cells) and 2, 2 and 1.7-fold (differentiated T-cells), respectively. E, Phospho-c-Jun accumulation in response to peptide-pulsed DCs. Cells were fixed and stained with anti-CD8 and anti-phospho-c-Jun-specific antibodies after the indicated stimulation periods. Although NRP-A7-induced differentiation resulted in heightened levels of basal phospho-c-Jun as compared to the background levels seen in naïve T-cells, NAT-32 and NRP-E6 induced phospho-c-Jun accumulation only in differentiated T-cells. Analyses were done on gated CD8+ T-cells. Top panels show representative staining patterns. Bottom panels show averages ± s.e.m. of 3-4 experiments/peptide/time point. MFI values from TUM-challenged cells were subtracted. P values shown correspond to differences vs. TUM at 24 h (for naïve T-cells) or 5h (for differentiated T-cells) (Mann-Whitney U).