Inhibition of T-tropic HIV infection of Mk precursors by SDF-1. Day 5 Mk culture cells were treated or not with 1 μg/mL SDF-1 and then inoculated with 0.1 m.o.i of NL4-3. HIV p24 production was measured through 9 days postinfection (p.i.) as described in Materials and Methods. (A) Percentage of p24 level decrease in SDF-1 treated from untreated (control values) Mks (mean ± SEM values from 3 independent experiments). (B) Infection inhibition results from a representative experiment. (▩), NL4-3; (▨), NL4-3 + SDF-1.