The CD85/LIR-1/ILT2 Inhibitory Receptor Is Expressed by All Human T Lymphocytes and Down-Regulates Their Functions

  • Saverino D
  • Fabbi M
  • Ghiotto F
  • et al.
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Abstract

The inhibitory molecule CD85/LIR-1/ILT2 has been detected previously on the surface of a small proportion of T lymphocytes. In this study, evidence is provided that, although only a fraction of CD3+ cells are stained by mAb specific for CD85/LIR-1/ILT2 on their surface, this inhibitory receptor is present in the cytoplasm of all T lymphocytes, and that it is detectable on the surface of all T cell clones by the M402 mAb. Biochemical analyses further demonstrate that CD85/LIR-1/ILT2 is present in all T clones analyzed, and that the protein is tyrosine-phosphorylated. Expression of mRNA coding for CD85/LIR-1/ILT2 has been assessed by RT-PCR. Notably, in the NKL cell line and in one T cell clone, amplification of the messenger required 30 cycles only, whereas, in other T cell clones, an amplification product was detected by increasing the number of cycles. CD85/LIR-1/ILT2 inhibits CD3/TCR-mediated activation in both CD4+ and CD8+ clones, and it down-regulates Ag recognition by CD8+ cells in a clonally distributed fashion. Addition of anti-ILT2 HP-F1 mAb in the cytolytic assay enhances target cell lysis mediated by Ag-specific CTL. This could be due to interference of the mAb with receptor/ligand interactions. In contrast, HP-F1 mAb cross-linking triggers inhibitory signals that reduce cytotoxicity. CD85/LIR-1/ILT2 also controls responses to recall Ags and, in low responders, its engagement sharply increases T cell proliferation. The inhibitory function of the molecule is also confirmed by its ability to reduce CD3/TCR-induced intracellular Ca2+ mobilization.

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APA

Saverino, D., Fabbi, M., Ghiotto, F., Merlo, A., Bruno, S., Zarcone, D., … Ciccone, E. (2000). The CD85/LIR-1/ILT2 Inhibitory Receptor Is Expressed by All Human T Lymphocytes and Down-Regulates Their Functions. The Journal of Immunology, 165(7), 3742–3755. https://doi.org/10.4049/jimmunol.165.7.3742

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