Figure 4

An Erk-Lck feedback loop regulates TCR-mediated signaling. A) Purified human T cells were treated with iAbs alone for 30 min and then either DMSO or the MEK inhibitor U0126 was added and incubated for an additional 30 to 60 min. Samples were analyzed by Western blotting using the indicated Abs. B) Bands in A) were quantified and the values were normalized as described. Graphs show the mean of the phosphorylation levels of Erk1/2, ZAP70, and LAT or the level of p59 Lck as arbitrary units ± SEM of 4 independent experiments. C) Purified human T cells were preincubated either in the presence of DMSO or the MEK inhibitor U0126 and subsequently stimulated with sAbs for the indicated time points. Samples were analyzed by Western blotting using the indicated Abs. D) Bands in C) were quantified as described above and the data from at least two independent experiments are shown.