Mouse primary lung fibroblasts (PLFs) were isolated from wild-type mice, and after passages 2–7, cells were treated with or without gp120 (10ng/mL). In a separate group, cells were pre-treated with AMD3100 (5μM) for 15 minutes prior to addition of gp120 (10ng/mL). Cells were then maintained in their respective treatment for the duration of the experiment. Cells were harvested at 120 minutes after treatment and analyzed for phosphorylated mitogen-activated protein kinase 1/2 (ERK1/2), total ERK1/2, and GAPDH protein expression. Graph depicts phosphorylation ERK1/2 normalized to total ERK1/2. Upper panel shows representative blots. N = 6 per group. *P<0.05 increased compared to untreated cells.