(A) Neutralization of HIV-tat activity by treatment with antibodies against HIV-tat. HIV-tat protein (100 ng/mL) was incubated with different dilution of the antibody for 1 hour at room temperature before its treatment with EC. The adhesion of EC to HL-60 was tested as described in Fig 6. All determinations were made in triplicate. (B) Potentiation of HIV-tat–induced adhesion of HL-60 cells to EC by TNF. EC were incubated with either HIV-tat (1 ng/mL) or TNF (100 ng/mL) or combination for 6 hours at 37°C and then examined for adhesion to HL-60 cells as described in Fig 6. All determinations were made in triplicate.