Differential effect of T cell membrane-associated cytokines in inducing IL-8, MCP-1, and IP-10. Fibroblasts were plated at 2 × 104 cells/well; 72 hours later the culture medium was replaced and T cell membranes corresponding to 2 × 105 cells generated from activated Th1 (panel a, n = 2; panel c, n = 4) and Th2 (panels b and c, n = 2) clones were added to the wells in triplicate cultures. Anti-TNF (soluble TNF receptor I; 10-8 mol/l), IL-1 receptor antagonist (2 μg/ml), anti-IFN-γ (10 μg/ml), anti-IL-4 (10 μg/ml), irrelevant monoclonal IgG1 (10 μg/ml) and IFN-γ (1,000 U/ml), alone or in combination, were added to the wells 30 minutes before T cell membranes. Chemokine levels were determined in the supernatants by enzyme-linked immunosorbent assay upon 48 hours of further culture. The bars represent the mean percentage ± standard error of chemokine production in the presence of T cell membranes without blocking agent. (a) IL-8 was 8.8 ± 1.9 ng/ml, MCP-1 was 4.7 ± 0.2 ng/ml and IP-10 was 7.3 ± 1.1 ng/ml. (b) IL-8 was 36.5 ± 8.8 ng/ml, MCP-1 was 6.6 ± 0.9 ng/ml and IP-10 was 0.8 ± 0.3 ng/ml. Note that basal IL-8 levels were fourfold lower and IP-10 tenfold higher in the presence of Th1 compared to Th2 cells. (c) With Th1 cells IL-8 was 6.9 ± 0.7 ng/ml; with Th2 cells IL-8 was 12.0 ± 2.2 ng/ml. *P < 0.05. IFN, interferon; IL, interleukin; IP, interferon-γ inducible protein; MCP, monocyte chemoattractant protein; Th, T-helper.