TCRVβ usage of altered peptide ligand-specific CD4+ T cells. TCRVβ usage of altered peptide ligand (APL)-specific CD4+ T cells was not remarkably shifted to TCRVβ8.1 8.2. Mice were immunized with 10 μg each APL, and draining lymph node cells on days 7 to 9 were stimulated with 20 μM corresponding APL in vitro. Ratios of TCRVβ repertoire to CD4+ T cells. The TCRVβ repertoire of CD4+ T cells was analyzed by flow cytometry: before stimulation with the corresponding in vitro for 72 hours, and after stimulation.