IL-6 downregulation of gp130 expression on T cells in a dose-dependent manner. Purified CD4⁺ and CD8⁺ splenic T cells from 6-week-old C57BL/6 mice were cultured with various concentrations of IL-6 for 2 days. Cells were washed and stained by RX19 or control rat myeloma IgG_2a. (A) CD4⁺ T cells. (B) CD8⁺ T cells.