CpG-ODN therapy increases resistance to growth factor withdrawal–induced death in naive T lymphocytes.

Purified T cells were obtained from untreated (■), CpG-ODN–treated (●), or Neg-ODN–treated (⋄) mice one day after the last ODN injection. T cells were purified from splenocytes and lymph nodes, and the naive T cells were further selected using anti-CD62L antibody coated magnetic beads. Purified naive CD4⁺ (A) or CD8⁺ (B) T cells were cultured separately in the absence of serum and exogenous cytokines for up to 12 hours. As a positive control, naive T cells from untreated mice were cultured in the presence of 5% FCS and 25 IU IL-2/mL (▵). The percent apoptotic cells were evaluated 6 and 12 hours after the initiation of the experiment by flow cytometry using annexin-V staining. (C) Purified naive T cells from Neg-ODN–treated mice were first labeled with CFSE and then mixed with an equal number of naive T cells (unlabeled) from CpG-ODN–treated mice. The cell mixture was placed in culture in medium lacking growth factors, and the numbers of viable CFSE-positive and CFSE-negative cells were estimated at various time points as described above. Error bars represent the standard errors of the means obtained from 3 different mice per group.