CTLA‐4 disrupts ZAP70 microcluster formation with reduced T cell/APC dwell times and calcium mobilization

Abstract

CTLA-4 is a co-receptor that modulates the threshold of T cell activation and autoimmunity. We previously showed that CTLA-4 reverses the TCR-mediated stop signal needed for T cell/APC interactions [Schneider et al., Science 2006, 313: 1972. In this study, using a different T cell system, we show that CTLA-4 expression changed the behavior of T8.1 T cells by reducing the contact time between T cell and APC, preventing re-inforced contacts, and reducing the contact area at the immunological synapse. This led to a major reduction in Ca 2+ influx/mobilization and interleukin-2 production. Further, anti-CD3/CTLA-4 increased T cell motility on antibody-coated glass slides, concurrent with an abrogation of ZAP70 microcluster formation. Our findings further support a role for CTLA-4 in limiting the interaction between T cell and APC that is needed for optimal activation.

Murine regulatory T cells differ from conventional T cells in resisting the CTLA-4 reversal of TCR stop-signal

“…8,21,22 The effect on motility and migration has now been reported by several other groups. [25][26][27] In this study, we reveal a clear difference in CTLA-4 modulation of the contact times and motility of Tconvs relative to Tregs.…”

“…8,21,22 However, these initial studies were performed using separated primary CTLA-4-positive and -negative T cells of normal mice and cell lines. 8,21,22 In a complementary approach, the motility and contact times of T cells from genetically ablated Ctla4 Ϫ/Ϫ mice were contrasted with cells from Ctla4 ϩ/ϩ DO11.10 Tg mice in LN slices in the presence of mature bone marrow (BM)-derived DCs 35,36 (Figure 1). Both sets of T cells were initially activated for 48 hours with plate-bound anti-CD3/CD28 to induce CTLA-4 expression on the Ctla4 ϩ/ϩ T cells.…”

“…20 In this context, we have shown that CTLA-4 induces T-cell motility (ie, motility activator) and limits contact times with DCs as well as affecting the migration of T cells in lymph nodes. 8,21,22 Reduced contact times by CTLA-4 would be expected to limit TCR ligation events and raise the threshold for T-cell activation. [21][22][23][24] The motility inducing effects of CTLA-4 have been confirmed by several laboratories in various in vivo models, [25][26][27] and involves CTLA-4 activation of the GTP binding protein Rap1 and LFA-1 adhesion.…”

“…5,6 CTLA-4 raises the threshold that is needed for T-cell activation by cell intrinsic and extrinsic pathways. 7 Cell intrinsic mechanisms include inhibition of ZAP-70 microcluster formation, 8 an altered immunologic synapse (IS), 9 modulation of TCR signaling by phosphatases SHP-2 and PP2A, 10,11 and interference with the expression or composition of lipid rafts on the surface of T cells. [12][13][14] Cell extrinsic functions include the ecto-domain competition for CD28 binding to CD80/CD86, 15 occupancy or removal of CD80/86 16 or the release of indoleamine 2,3-dioxygenase (IDO) 17 and transforming growth factor ␤ (TGF-␤).…”

PD-1 and CTLA-4 Mediated Inhibitory Signaling for T cell Exhaustion during Chronic Viral Infections

“…Ligation of CTLA-4 reduces the contact time between DC and T cells and prevents immunological synapse formation. This leads to a major reduction in Ca 2+ influx/mobilization and an abrogation of ZAP70 microcluster formation [59]. It was also suggested that CTLA-4 regulates T cell adhesion and promotes T cell mobility, possibly in a RAP1-dependent way [60].…”