Fig. 1

Effects of cysteinyl leukotrienes on histamine hyperresponsivity in human umbilical smooth muscle cells (A), immortalized 4/4 murine macrophages (B), and freshly isolated human monocytes (C). Cells were stimulated with different concentrations of histamine in the absence (open circles) or presence (filled circles) of 100 ng/ml LTD₄ (A) or 100 ng/ml LTE₄ (B,C) for 1 hr. The histamineinduced PGE₂ production was used as a functional measure to determine the histamine responses in these cells. Results represent the mean and standard error of four independent experiments. Statistically significant differences were calculated using the t-test; *p < 0.05 and **p < 0.01.