Fig. 3.

Relationship of IL-6 and IL-10 productions in metastatic melanoma cells. a IL-6 production by fresh metastatic melanoma cell suspensions. Three fresh metastatic melanoma cell suspensions produced high levels of IL-6 (>1,000 pg/ml, high IL-6 producers, solid bars), while seven suspensions produced small or no quantity of IL-6 (low IL-6 producers, open bars) in 18-h culture. b Increased IL-10 production by fresh metastatic melanoma cell suspensions in response to exogenously added IL-6. Fresh metastatic melanoma cell suspensions were cultured with various concentration of rhIL-6. “Control, 0 ng/ml” indicates constitutive production of IL-10 without IL-6 stimulation. Two of 7 low IL-6 producers (DIL and Ho88) produced IL-10 constitutively and increased IL-10 production in response to exogenously added IL-6 in a dose-dependent manner. The rest of low IL-6 producers had minimum or no constitutive production of IL-10 and did not responded to exogenously added IL-6. All three high IL-6 producers (Cla, Beu, Ho91) constitutively secreted IL-10 with mild increase in IL-10 production in response to high dose of IL-6. *P < 0.05, **P < 0.01. c Maintaining IL-6-induced IL-10 production in long-term cultured metastatic melanoma cell lines. Two cell lines (DIL and Ho88) established from low IL-6 producers maintained their capability of producing IL-10 in response to exogenously added IL-6 in a dose-dependent manner. The cell line, Beu, established from a high IL-6 producer continued to produce the high amount of IL-6 and responded to exogenous IL-6 only at the highest dose (20 ng/ml). In contrast, the two cell lines (Cr and Cla) did not produce IL-10 and did not respond to IL-6. *P < 0.05, **P < 0.01