Blunted responses to S1P in the HIV-1+ lymph node. S1P responses were assessed in cell suspensions prepared from lymph nodes of HIV-1+ patients and uninfected controls. (A) S1P-induced Akt phosphorylation. (B) SDF-induced Akt phosphorylation. (C) S1P-induced actin polymerization. (D) SDF-induced actin polymerization. Actin pol., actin polymerization; CM, central memory; EM effector memory,