CD8+ lymphocyte Cyclin E production in FIV+ and FIV- cats following CD4+CD25+ co-culture. Cyclin E production begins during late G1 phase and peaks during early to mid S phase. CD8+ LN cells from either FIV+ (left) or FIV- (right) cats were either untreated (first column) or co-cultured with autologous CD4+CD25+ Treg cells (second column). Shown above is a representative blot for experiments from FIV+ (n = 4) and FIV- (n = 2) cats. The mean cyclin E production was increased greater than two-fold in FIV+ cats following a twelve hour CD4+CD25+ co-culture and decreased approximately one-fold in FIV- cats.