Irradiated splenocytes that were used as a source of APCs in our experiments could

be treated with Ficoll–Hypaque and separated from the CD4+ T cells only after 1 day in cultures. In preparation for later experiments, Fig. 1(c) was included, showing that anergy could be demonstrated using beads instead of antigen to stimulate secondary cultures. In addition to proliferative unresponsiveness, Th1 cells stimulated with antigen in the presence of n-butyrate demonstrated a 37–77% decrease in IL-2 and a 26–55% decrease in interferon-γ secretion when stimulated in secondary culture with three different stimulation indices (Fig. 1d). Hence, n-butyrate-induced anergy Ku-0059436 concentration was demonstrated by a loss of both antigen-induced proliferation and cytokine production. It has

been reported previously that n-butyrate increased p21Cip1expression in antigen-stimulated Th1 cells.8 However, p21Cip1 is also induced in antigen-stimulated Th1 cells in the absence of n-butyrate. Consequently, the kinetics of p21Cip1 up-regulation was studied in antigen-stimulated Th1 cells in the presence and absence of n-butyrate during the 6-day primary cultures to compare the two groups for PD0332991 in vivo any possible difference in p21Cip1 expression. When antigen was added in the initiation of the primary culture (day 0), p21Cip1 was up-regulated in control Th1 cells by day 1, remained high on day 2, but decreased significantly by day 3 and was back to resting levels by day 5 (Fig. 2a). In contrast, when antigen was added on day 0 and n-butyrate was added on day 1, the p21Cip1 levels remained

elevated in anergic Th1 cells during the entire 6-day primary culture. p27Kip1 is another cdk inhibitor thought to play a role in T-cell anergy. As expected, p27Kip1 was high in resting Th1 cells. Its level decreased with the antigen stimulation and was later restored to resting levels in control Th1 cells by day 5 of the primary cultures. In contrast, p27Kip1 levels failed to be completely restored in Th1 cells incubated with antigen and n-butyrate in 6-day primary cultures (Fig. 2b). Hence, because p21Cip1 rather than p27Kip1 was high in the anergic Th1 cells at the end of the 6-day primary cultures, subsequent experiments OSBPL9 were focused on the role of p21Cip1 in maintaining proliferative unresponsiveness. The kinetics of other cell cycle proteins was also studied to assess their possible involvement in n-butyrate-induced T-cell anergy. No significant differences between the antigen-stimulated control and anergic Th1 cells were observed in the expression of cdk2, cdk4, cdk6, cyclin D2, cyclin D3 and cyclin E (Fig. 2b). In summary, the kinetics studies on cell cycle proteins revealed that the most detectable difference between anergic and control Th1 cells was the high level of p21Cip1 maintained throughout the primary cultures in the anergic Th1 cells. Localization of proteins such as p21Cip1 in the cell can have important functional consequences.