Reconstitution of deficient T cell receptor ζ chain restores T cell signaling and augments T cell receptor/CD3–induced interleukin‐2 production in patients with systemic lupus erythematosus

Abstract

Objective. T cells from a majority of patients with systemic lupus erythematosus (SLE) display antigen receptor-mediated signaling aberrations associated with defective T cell receptor (TCR) chain, a subunit of the TCR/CD3 complex. This study was undertaken to explore the possibility that forced expression of TCR chain may reverse the known signaling abnormalities and defective interleukin-2 (IL-2) production in SLE T cells.Methods. Freshly isolated SLE T cells were transfected with TCR chain construct in a eukaryotic expression vector at high efficiency, by a recently developed nucleoporation technique. Restoration of TCR/ CD3-mediated signaling was studied in the chaintransfected cells.Results. In SLE T cells transfected with TCR chain, surface expression of TCR chain was increased and the TCR/CD3-induced increased free intracytoplasmic calcium concentration response was normalized, as was hyperphosphorylation of cellular substrates. Simultaneously, the previously noted increased expression of the Fc receptor ␥ chain was diminished in SLE T cells transfected with the chain expression vector, and the surface membrane clusters of cell signaling molecules were redistributed to a more continuous pattern. TCR chain replacement also augmented the expression of diminished TCR/CD3-mediated IL-2 production in SLE T cells, associated with increased expression of the p65 subunit of nuclear factor B in the nuclear fractions of these T cells. Conclusion. These results suggest that reconstitution of deficient TCR chain can reverse the TCR/ CD3-mediated signaling abnormalities as well as the defective IL-2 production in T cells of patients with SLE.It is well recognized that T cells from patients with systemic lupus erythematosus (SLE) display a number of signaling abnormalities (1). Many of the identified molecular aberrations explain certain established cell and cytokine defects, whereas the mechanisms of other defects have not yet been elucidated. Our group and others have demonstrated that the expression of the subunit of the T cell receptor (TCR) is decreased in a majority of SLE patients (2-4) and that this defect persists over time and is independent of disease activity (5).Despite the decreased expression of the TCR chain in SLE T cells, crosslinking of the TCR/CD3 complex leads to increased free intracytoplasmic calcium concentration ([Ca 2ϩ ] i ) response (6) and protein tyrosine phosphorylation (2,4). These events appear to occur because the Fc receptor (FcR) ␥ chain becomes a functional part of the TCR/CD3 complex (7). In support

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