Induction of MCP-1 mRNA and protein by IL-6 and LPS in PBMCs. One HIV-negative and one HIV-positive individual are shown. PBMCs were cultivated for 24 hours with medium alone (control), IL-6 (0.24 nmol/L), or LPS (1 μg/mL). (A) The cells were pelletted and frozen until processed for RT-PCR analysis of MCP-1 mRNA compared with the levels of expression of the housekeeping gene GAPDH. (B) Cell culture supernatants were harvested and frozen at −80°C until tested for MCP-1 protein content by ELISA. Similar results were obtained with PBMCs from two additional HIV-negative and two HIV-seropositive individuals cultured under the same conditions for 24 hours. (□) Unstimulated; (▪) IL-6 (0.24 nmol/L); (▨) LPS (1 μg/mL).