Chronic TNF-α exposure impairs TCR-signaling via TNF-RII but not TNF-RI

Chronic exposure to TNF-α has been shown to impair T cell-activation in mice and in humans. In the present study, we investigated a possible role of TNF-RII in this long-term effect of TNF-α. Chronic TNF-α exposure led to suppression of subsequent TCR stimulation (e.g., TCR/CD28-induced proliferation, cytokine production (IFN-γ, TNF-α)) but left TCR independent restimulation unaffected. Activation of T cells during TNF-α exposure was required for the inhibitory effect on TCR stimulation. In contrast to the mouse model, the inhibitory effect of long-term TNF-α exposure was mediated via TNF-RII but not TNF-receptor I, and surface expression of the TCR/CD3 complex remained unchanged. Chronic TNF-RII triggering downregulated T cell activation at an early level, as TCR-induced calcium flux and IL-2 mRNA expression were impaired after preculture in the presence of anti-TNF-RII mAbs. Furthermore, chronic TNF-RII-stimulation specifically downregulated store operated calcium channels, which contribute to sustained TCR-induced calcium influx.