Soluble CD4 (sCD4) inhibits HIV-induced L-selectin shedding on resting CD4⁺ T cells. HIV-1 NL4-3–infected (thick lines) or mock-infected (thin lines) Jurkat cells (2 × 10⁶) were treated with medium, 10 μg/mL soluble CD4, or 10 μg/mL BSA at 37°C for one hour, and cocultured with 2 × 10⁶ CFSE-labeled human CD4⁺ T cells at 37°C for 16 to 20 hours. The expression of L-selectin and CD69 on CFSE⁺ cells was determined by flow cytometry.