CD160 is a glycosylphosphatidylinositol (GPI)-anchored protein member of the Ig superfamily with a restricted expression profile that is limited to CD56dim CD16+ NK cells, NKT-cells, γδ T-cells, cytotoxic CD8+ T-cells lacking the expression of CD28, a small fraction of CD4+ T cells and all intraepithelial lymphocytes. Binding of CD160 to both classical and non-classical MHC I enhances NK and CD8+ CTL functions. However, engagement of CD160 by the Herpes Virus Entry Mediator (HVEM / TNFRSF14) was shown to mediate inhibition of CD4+ T-cell proliferation and TCR-mediated signaling.
HVEM protein is a bimolecular switch that binds both co-stimulatory LT-α/LIGHT and co-inhibitory receptors BTLA/CD160. The ligation of coinhibitory receptors BTLA and/or CD160 on T cells with HVEM expressed on DC or Tregs transduces negative signals into T cells that are counterbalanced by costimulatory signals delivered after direct engagement of HVEM on T cells by LIGHT expressed on DC or more likely, on other activated T cells (T–T cell cooperation). The predominance of the interaction of HVEM with BTLA and CD160 over the HVEM/LIGHT pathway or vice versa might be the result of differences in ligand/receptor affinity and the differential expression pattern of these molecules on cell types at different stages of cell differentiation. LIGHT, BTLA, and CD160 have substantially different binding affinities and occupy spatially distinct sites upon interaction with the HVEM receptor, which enables HVEM to function as a molecular switch. The net effect of the LIGHT/HVEM and HVEM/BTLA/CD160 interaction, when these different receptors and ligands are simultaneously present, determines the outcome of the response.
M. L. del Rio. HVEM/LIGHT/BTLA/CD160 cosignaling pathways as targets for immune regulation. Journal of Leukocyte Biology. 2010;87.