Abstract
Ephrins (EFN) are cell-surface ligands of Ephs, the largest family of cell-surface receptor tyrosine kinases. The function of EFNs in the immune system has not been well studied, although some EFNs and Ephs are expressed at high levels on certain leukocytes. We report here that EFNB3 and its receptors (collectively called EFNB3Rs, as EFNB3 binds to multiple EphBs) were expressed in peripheral T cells and monocytes/macrophages, with T cells being the dominant EFNB3+ and EFNB3R+ cell type. Solid-phase EFNB3-Fc in the presence of suboptimal anti-CD3 crosslinking enhanced T-cell responses in terms of proliferation, activation marker expression, interferon-gamma but not interleukin-2 production, and cytotoxic T-cell activity. EFNB3R costimulation in the presence of phorbol 12-myristate 13- acetate was insensitive to cyclosporin A, similar to CD28 costimulation, suggesting they might share a part of the signaling pathway. After crosslinking, T-cell receptor and EFNB3R congregated into aggregated rafts, and this provided a morphological basis for signaling pathways of T-cell receptor and EFNB3R to interact. Solid-phase EFNB3-Fc augmented p38 and p44/42 MAPK activation further downstream of the signaling pathway. These data suggest that EFNB3 is important in T-cell/T-cell and T-cell/antigen-presenting cell collaboration to enhance T-cell activation and function.
Highlights
Full T-cell activation requires costimulation in addition to T-cell receptor (TCR)1 ligation
We have reported that EFNB3 and EFNB3Rs were expressed in T cells and monocytes/macrophages
T cells costimulated by solid-phase EFNB3-Fc in the presence of suboptimal anti-CD3 showed enhanced proliferation and Cytotoxic T Lymphocyte (CTL) activity, production of IFN-␥ but not IL-2, and expression of certain T-cell activation markers, such as CD69
Summary
Full T-cell activation requires costimulation in addition to T-cell receptor (TCR)1 ligation. Solid-phase EFNB3-Fc in the presence of suboptimal anti-CD3 crosslinking enhanced T-cell responses in terms of proliferation, activation marker expression, interferon-␥ but not interleukin-2 production, and cytotoxic T-cell activity. We investigated the expression of EFNB3 and its receptors in immune cells and explored its function in regulating T-cell activity.
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