Non-classical major histocompatibility class Ib molecule involved in immune regulatory processes at the maternal-fetal interface (PubMed:23184984, PubMed:29262349, PubMed:19304799). In complex with B2M/beta-2 microglobulin binds a limited repertoire of nonamer self-peptides derived from intracellular proteins including histones and ribosomal proteins (PubMed:7584149, PubMed:8805247). Peptide-bound HLA-G-B2M complex acts as a ligand for inhibitory/activating KIR2DL4, LILRB1 and LILRB2 receptors on uterine immune cells to promote fetal development while maintaining maternal-fetal tolerance (PubMed:23184984, PubMed:29262349, PubMed:16366734, PubMed:19304799, PubMed:20448110, PubMed:27859042). Upon interaction with KIR2DL4 and LILRB1 receptors on decidual NK cells, it triggers NK cell senescence-associated secretory phenotype as a molecular switch to promote vascular remodeling and fetal growth in early pregnancy (PubMed:23184984, PubMed:29262349, PubMed:16366734, PubMed:19304799). Through interaction with KIR2DL4 receptor on decidual macrophages induces pro-inflammatory cytokine production mainly associated with tissue remodeling (PubMed:19304799). Through interaction with LILRB2 receptor triggers differentiation of type 1 regulatory T cells and myeloid-derived suppressor cells, both of which actively maintain maternal-fetal tolerance (PubMed:20448110, PubMed:27859042). May play a role in balancing tolerance and antiviral-immunity at maternal-fetal interface by keeping in check the effector functions of NK, CD8+ T cells and B cells (PubMed:10190900, PubMed:11290782, PubMed:24453251). Reprograms B cells toward an immune suppressive phenotype via LILRB1 (PubMed:24453251). May induce immune activation/suppression via intercellular membrane transfer (trogocytosis), likely enabling interaction with KIR2DL4, which resides mostly in endosomes (PubMed:20179272, PubMed:26460007). Through interaction with the inhibitory receptor CD160 on endothelial cells may control angiogenesis in immune privileged sites (PubMed:16809620). Likely does not bind B2M and presents peptides. Negatively regulates NK cell- and CD8+ T cell-mediated cytotoxicity (PubMed:11290782). Likely does not bind B2M and presents peptides. Negatively regulates NK cell- and CD8+ T cell-mediated cytotoxicity (PubMed:11290782). Likely does not bind B2M and presents peptides. Negatively regulates NK cell- and CD8+ T cell-mediated cytotoxicity (PubMed:11290782). Non-classical major histocompatibility class Ib molecule involved in immune regulatory processes at the maternal-fetal interface (PubMed:23184984, PubMed:29262349, PubMed:19304799). In complex with B2M/beta-2 microglobulin binds a limited repertoire of nonamer self-peptides derived from intracellular proteins including histones and ribosomal proteins (PubMed:7584149, PubMed:8805247). Peptide-bound HLA-G-B2M complex acts as a ligand for inhibitory/activating KIR2DL4, LILRB1 and LILRB2 receptors on uterine immune cells to promote fetal development while maintaining maternal-fetal tolerance (PubMed:23184984, PubMed:29262349, PubMed:16366734, PubMed:19304799, PubMed:20448110). Upon interaction with KIR2DL4 and LILRB1 receptors on decidual NK cells, it triggers NK cell senescence-associated secretory phenotype as a molecular switch to promote vascular remodeling and fetal growth in early pregnancy (PubMed:23184984, PubMed:29262349, PubMed:16366734, PubMed:19304799). Through interaction with KIR2DL4 receptor on decidual macrophages induces pro-inflammatory cytokine production mainly associated with tissue remodeling (PubMed:19304799). Through interaction with LILRB2 receptor triggers differentiation of type 1 regulatory T cells and myeloid-derived suppressor cells, both of which actively maintain maternal-fetal tolerance (PubMed:20448110). Reprograms B cells toward an immune suppressive phenotype via LILRB1 (PubMed:24453251). Likely does not bind B2M and presents peptides. Likely does not bind B2M and presents peptides. Forms a heterotrimer with B2M and a self-peptide (peptide-bound HLA-G-B2M) (PubMed:7584149, PubMed:8805247). HLA-G-B2M complex interacts with components of the antigen processing machinery TAPBP and TAP1-TAP2 complex; this interaction is required for loading of high affinity peptides and heterotrimer translocation to the cell surface (PubMed:7584149). Interacts with CALCR; this interaction is required for appropriate folding (PubMed:9640257). Interacts with COPB1; this interaction mediates the endoplasmic reticulum (ER) retrieval of HLA-G-B2M complexes that bind low affinity peptides (PubMed:11520457, PubMed:12582157). On the cell surface, peptide-bound HLA-G-B2M molecules (referred to as monomers) can form disulfide-linked homomultimers, homodimers and homotrimers (PubMed:12454284, PubMed:12874224, PubMed:16455647). Interacts with KIR2DL4; this interaction is direct (PubMed:10190900, PubMed:16366734). Interacts with LILRB1 and LILRB2 receptors; this interaction is direct (PubMed:16455647, PubMed:16366734, PubMed:17056715, PubMed:12853576). Interacts with CD160; this interactions is direct (PubMed:16809620). Interacts with CD8A homodimer; this interaction is direct and might down-regulate T cell receptor signaling (PubMed:12853576). Isoform 2: Forms a non-disulfide-linked homodimer and interacts with LILRB2 (PubMed:28348268). HLA-G trogocytosis from extravillous trophoblast's filopodia occurs in the majority of decidual NK cells. Expressed in adult eye (PubMed:1570318). Expressed in immune cell subsets including monocytes, myeloid and plasmacytoid dendritic cells and regulatory T cells (Tr1)(at protein level) (PubMed:20448110). Secreted by follicular dendritic cell and follicular helper T cells (PubMed:24453251). Isoform 5: Detected in physiological fluids including amniotic fluid and serum (PubMed:11137219). Isoform 7: Expressed in placenta, amniotic membrane, skin cord blood and peripheral blood mononuclear cells (PubMed:11137219). Expressed at the morula stage (at protein level) (PubMed:29262349). Expressed in extravillous trophoblast and cytotrophoblast (PubMed:26460007, PubMed:16210391, PubMed:7589701). Expressed in fetal eye and thymus (PubMed:2336406). Isoform 7: Expressed in fetal liver (PubMed:11137219). Up-regulated by immunosuppressive cytokine IL10 on dendritic cells and CD4+ T cells (PubMed:20448110). Up-regulated by progesterone in cytotrophoblasts (PubMed:16210391). N-glycosylated. Produced by proteolytic cleavage at the cell surface (shedding) by matrix metalloproteinase MMP2. Belongs to the MHC class I family.