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Table 1 B7/B7 ligand family members and functions

From: Immune checkpoint receptors in regulating immune reactivity in rheumatic disease

Molecule Expression Ligand/receptor Function
CD28 Resting T cells CD80 or CD86 on APCs Lowers TCR threshold
    Delivers a co-stimulatory signal
    Promotes T-cell proliferation, survival, cytokine production, T cell-dependent B cell functions [2]
CTLA-4/CD152 Resting/activating T cells Outcompetes CD28 for CD80/CD86 binding Increased TCR threshold
    Delivers a co-inhibitory signal [2]
    Upregulates indoleamine 2,3-dioxygenase
    CTLA-4-/- mice develop autoimmunity [2]
PD-1/CD279 T cells, B cells, DCs, monocytes, NK T cells, exhausted cells and Tregs PD-L1 on APCs, B cells, and T cells. PD-L2/CD273 on APCs. PD-L1/CD274 can also bind to CD80 Delivers an inhibitory signal
    Suppresses Bcl-xl [2]
ICOS/CD278 Activated T cells, T follicular helper cells ICOSL/CD275 on APCs and B cells [2] Induces proliferation
    Propagates germinal center reactions
    Upregulates IL-10 production [2]
BTLA/CD272 B cells, DCs, Th1 cells, macrophages Herpes virus entry mediator [2] BTLA delivers an inhibitory signal via ITIM and ITSM [2]
B7-H3/CD276 B cells, NK cells, T cells, activated monocytes [2] Unknown Co-inhibitory and co-stimulatory functions. Suppress antitumor responses [2]
B7-H4/B7S1/B7x/Vtcn1 APCs, cancer cells, and mRNA expression on nonhematopoietic tissue [2] Unknown Reduces cell proliferation and T cell interleukin-2 production [2]
B7-H6 Tumor cells [3] NKp30 Binds NKp30 on NK cells resulting in interferon gamma and cytotoxic function [2]
VISTA/Dies1/Gi24/PD-1H Highly expressed on murine myeloid cells. Low expression on T cells [2] Unknown Inhibits T-cell proliferation, reduces CD44 and CD69 expression [2]
    Increases cell motility [2]
  1. APC, antigen presenting cell; BTLA, B and T lymphocyte attenuator; CTLA-4, cytotoxic T lymphocyte antigen-4; DC, dendritic cell; ICOS, inducible co-stimulator; ICOSL, inducible co-stimulator ligand; ITIM, immunoreceptor tyrosine-based inhibition motif; ITSM, immunoreceptor tyrosine-based switch motif; NK, natural killer; PD-1, programmed death-1; PD-L, programmed death ligand; TCR, T-cell receptor; Th, T helper; Treg, regulatory T cell.