CD69 expression and impaired T-cell responsiveness to S1P. Cell surface expression of CD69 and its relationship to S1P responsiveness was assessed in LN T-cells. (A) Impaired S1P induction of Akt phosphorylation and actin polymerization in CD69⁺ LN T-cells. This is representative of 13 samples from both HIV− and HIV+ donors. (B) S1P-induced Akt phosphorylation and actin polymerization in CD69 positive and CD69 negative LN cells. Actin pol., actin polymerization.