Vav1^−/− T cells are not susceptible to antigen-induced stop signals. (A) HY-specific A^b-restricted WT and Vav1^−/− T cells were incubated with plastic bound anti-CD3 and anti-CD28 for 45 minutes and plated on rICAM-1–coated transwells. As a control, T cells were exposed to hamster Ig isotype control or medium alone. Migration was measured as indicated in the legend to Figure 1. The percentage of migrated cells was calculated by dividing the number of cells in the lower chamber with the number of cells plated on the transwells. Error bars indicate standard error (** P < .01, *** P < .001). (B) DCs were obtained from bone marrow of syngeneic female mice (fDCs) and cultured for 7 days in GM-CSF, followed by overnight LPS-induced maturation. HY-specific A^b-restricted CD4⁺ PKH26-labeled WT or Vav1^−/− T cells were incubated with CFSE-labeled female-derived DCs pulsed with 50 nM Dby peptide for 2 hours (fDCs Dby). Nonantigenic DCs (fDCs) were used as a control. Conjugate formation was analyzed by flow cytometry as described in “DC/lymphocyte conjugate formation assays.” The mean percentage of conjugate formation from 4 experiments is shown in panel C. Error bars indicate standard error (**P < .01, ***P < .001).