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

The functional receptor for the inflammatory cytokine IL-6 is composed ofthe ligand binding IL-6 receptor alpha chain (IL-6R alpha) and the signaltransducing chain gp130, which is a shared component of multiple cytokinereceptors. We analyzed the surface expression of gp130 and IL- 6R alpha inthymocytes and peripheral T cells. While all thymocytes expressed gp130throughout thymic maturation, they gained expression of IL-6R alpha at theCD4 or CD8 single-positive stage. Approximately 10- 30% of the CD4-CD8+ and40-50% of the CD4+CD8- thymocytes expressed IL- 6R alpha. Within theCD4+CD8- population, the IL-6R alpha- subpopulation was cortisonesensitive, appeared immature according to the cell surface markersexpressed and failed to proliferate after TCR cross-linking. Peripheral Tcells were predominantly gp130+ and IL-6R alpha+, but down-regulated gp130and IL-6R alpha expression upon TCR engagement in vitro and in vivo.Peripheral gp130low/-IL-6R alphalow/- T cells expressed surface markerscharacteristic of memory T cells. We show that gp130 and IL-6R alpha areexpressed in a regulated manner in T cells, depending on the developmentaland functional stage.