7b). Antibody stimulation was used instead of antigen stimulation to demonstrate the direct effect of Y-27632 research buy the inhibitor on

Th1 cells and to discount the indirect effects on APCs. Inhibition of JNK activity by SP600125 was sufficient to suppress the proliferation of the KLH-specific Th1 cells, indicating that Th1 cells used in this model are no different from primary CD4+ T cells in that the inhibition of JNK alone is sufficient to block proliferation. In conclusion, p21Cip1-mediated suppression of JNK activity in anergic Th1 cells is a novel potential mechanism that could account for the proliferative unresponsiveness found in these cells. This manuscript examined the role of p21Cip1 in maintaining the proliferative unresponsiveness found Selleckchem Raf inhibitor in Th1 cells anergized by exposure to antigen and n-butyrate. The results presented in this work suggest that p21Cip1 functions in these Th1 cells primarily through the inhibition of members of the MAPK family rather than inhibition of its classical interaction partners,

namely cdk. p21Cip1 has long been described as a negative regulator of the cdk-mediated G1 to S phase transition.25 However, based on the association pattern of p21Cip1 and cdk in anergic compared to control Th1 cells, the p21Cip1 inhibition of cdk activity does not appear to be the primary mechanism for cell cycle inhibition. Instead, the results suggest that p21Cip1 specifically interacts with p-JNK and p-c-jun in antigen-restimulated anergic Th1 cells. The role of p21Cip1 in the normal cell cycle has been at

variance in different studies. Eventually, a dual role has been suggested for p21Cip1 in which low levels of p21Cip1 facilitated the cell cycle by promoting cdk–cyclin complex assembly whereas high levels inhibited cdk activity.25–27 The role of p21Cip1 in normal T-cell activation is not clear. T cells from the p21Cip1-deficient mice exhibited enhanced homeostatic proliferation and increased Acyl CoA dehydrogenase the frequency of cycling T cells.28 Another study using p21Cip1-deficient mice reported that p21Cip1 did not affect primary proliferation of naïve T cells, but was required for the regulation of activated/memory T-cell proliferation.29 In the present study, control Th1 cells stimulated for 36 hr with antigen contained appreciable amounts of p21Cip1, much of which associated with cdk2, cdk4 and cdk6. It would therefore seem likely that at least some of the regulatory effect of p21Cip1 in stimulated control Th1 cells in our system involves interaction with cdk. The amount and timing of p21Cip1 induced in activated T cells may be sufficient to promote cdk–cyclin assembly but not enough to block cdk activity. Alternatively, p21Cip1 may be up-regulated in activated T cells as a fail-safe mechanism in case some kind of cellular stress necessitates regulation of DNA replication or repair.