Fig. 2.

Systemic application of IL-33 increases pulmonary melanoma metastases. a Mice (n = 9–11) were injected intravenously with 0.5 × 10⁵ B16-F1 and treated intraperitoneally with IL-33 or PBS. b Representative photographs of lungs from melanoma-bearing mice injected with IL-33 or PBS. c, d Occurrence and average number of metastases. e, f Average size and size distribution of metastases. g Relative mRNA ST2 expression in B16-F1 cells. GAPDH mRNA was used as an internal control. Data are presented as mean ± SE fold of control in B16-F1 cells. h, i Immunohistochemical analysis of IL-33 expression in B16-F1 primary tumor cells and immune cells in metastatic lungs. j Representative photographs of IL-33 expression (magnification at × 400). k, l Immunohistochemical analysis of ST2 expression in B16-F1 metastatic cells and immune cells in metastatic lungs. m Representative images of ST2 expression (magnification at × 400). n Determination of IL-33 serum levels in melanoma patients and healthy volunteers (n = 20–30 per group). Data are presented as mean ± SE of all samples in each group, *p < 0.05, **p < 0.01. IP: intraperitoneal; IV: intravenous