sessing the percentage of NP-APC /CD38-PElo/PNA-FITChi host B cells, multiplied by the total number of live lymphocytes that were recovered from the spleen. Serum samples were analyzed by ELISA for the presence of NP-specific IgG1. In vivo effector generation. 106 naive AND TCR Tg GFP CD4 T cells were mixed with 2 105 PCCF peptide-pulsed DCs and transferred i.v. into intact B10.Br mice. Subsequently, 2 105 DCs without PCCF peptide (acute stimulation) or 2 105 PCCF peptide-pulsed DCs (RS) were transferred on days 1–4. Alternatively, 2 106 naive HNT TCR Tg CD4 T cells were mixed with 2 106 HNT peptide-pulsed DCs and trans- ferred i.v. into intact B10.Br mice. Subsequently, 2 106 DCs without HNT peptide (acute stimulation) or 2 106 HNT peptide-pulsed DCs (RS) were transferred on days 1–4. The numbers of naive CD4 T cells and peptide pulsed DCs were titrated to ensure optimal CD4 effector responses under conditions of acute stimulation. 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