MHC II accumulation during superantigen-mediated T cell stimulation differs significantly between vav+/+ and vav−/− cells and to a lesser extent between vav+/+ and vav+/− cells. I-Ek-GFP transfected A20 B cell lymphoma cells were loaded with 10 μM SEA or SEE and were used to stimulate either vav+/+, vav+/−, or vav−/− T cells. The I-Ek–GFP accumulation at the T cell/APC interface was analyzed as described in Fig. 2. The number of T cell/APC couples analyzed in each experiment for vav+/+, vav+/−, and vav−/− cells is n = 33, n = 30, and n = 35, respectively. The data are derived from three independent sets of experiments.