Regulated expression of gp130 and IL-6 receptor α chain in T cell maturation and activation

The functional receptor for the inflammatory cytokine IL-6 is composed of the ligand binding IL-6 receptor a chain (IL-6R alpha) and the signal transducing chain gp130, which is a shared component of multiple cytokine receptors. We analyzed the surface expression of gp130 and IL-6R alpha in thymocytes and peripheral T cells. While ail thymocytes expressed gp130 throughout thymic maturation, they gained expression of IL-6R alpha at the CD4 or CD8 single-positive stage. Approximately 10-30% of the CD4(-)CD8(+) and 40-50% of the CD4(+)CD8(-) thymocytes expressed IL-6R alpha. Within the CD4+CD8- population, the IL-6R alpha(-) subpopulation was cortisone sensitive, appeared immature according to the cell surface markers expressed and failed to proliferate after TCR cross-linking. Peripheral T cells were predominantly gp130(+) and IL-6R alpha(+), but downregulated gp130 and IL-6R alpha expression upon TCR engagement in vitro and in vivo. Peripheral gp130(low/-)IL-6R alpha(low/-) T cells expressed surface markers characteristic of memory T cells, We show that gp130 and IL-6R alpha are expressed in a regulated manner in T cells, depending on the developmental and functional stage.