A summary of the relative production levels of Cyclins D and E, the CDKI p21cip1, and Rb in CD8+ lymphocytes from FIV+ and FIV- cats following CD4+CD25+ co-culture. FIV+ cats exhibit a decrease in cyclin D3 with increases in both cyclin E and p21cip1. This pattern is consistent with a cell that is in either late G1 or early S phase of the cell cycle (as shown in Figure 1). The lack of Rb phosphorylation suggests that the CD8+ lymphocytes from FIV+ cats are in late G1 cell cycle arrest following co-culture with activated CD4+CD25+ lymphocytes. For FIV+ cats, each bar represents the mean (+ SEM) of four separate experiments, for FIV- cats each bar represents the mean of two separate experiments.