In vivo Th development in Vav1^–/– mice. (A-B) Groups of 3 wild-type mice (○) or 3 Vav1^–/– mice (•) were primed subcutaneously with 100 μg KLH given either in IFA (A) or in CFA (B). On day 10, the draining periaortic and inguinal lymph node cells were stimulated in vitro with the indicated KLH concentrations in triplicate. Proliferation and cytokine production were determined as in Figure 2. All data are expressed as the mean value of triplicate determinations ± SE. (C) Spleen cells from mice immunized as in panel B were stimulated with 1 μg/mL KLH, and IFN-γ– producing cells were enumerated by ICCS 16 hours later. The data shown are representative of 3 independent experiments.