Figure 5

CD8⁺ lymphocyte Rb phosphorylation in FIV⁺ and FIV^- cats following CD4⁺CD25⁺ co-culture. Hyperphosphorylation of Rb by cyclin/CDK complexes and subsequent separation of E2F proteins from Rb signals the irreversible commitment of the cell to S phase; while lack of Rb phosphorylation suggest either quiescence (G₀) or anergy (G₁ cell cycle arrest). As depicted here, 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. There was a lack of Rb phosphorylation in both FIV⁺ and FIV^- cats following an eighteen hour CD4⁺CD25⁺ co-culture.