RESUMO
DAP12, an immunoreceptor tyrosine-based activation motif-bearing adapter protein, is involved in innate immunity mediated by natural killer cells and myeloid cells. We show that DAP12-deficient mouse B cells and B cells from a patient with Nasu-Hakola disease, a recessive genetic disorder resulting from loss of DAP12, showed enhanced proliferation after stimulation with anti-IgM or CpG. Myeloid-associated immunoglobulin-like receptor (MAIR) II (Cd300d) is a DAP12-associated immune receptor. Like DAP12-deficient B cells, MAIR-II-deficient B cells were hyperresponsive. Expression of a chimeric receptor composed of the MAIR-II extracellular domain directly coupled to DAP12 into the DAP12-deficient or MAIR-II-deficient B cells suppressed B cell receptor (BCR)-mediated proliferation. The chimeric MAIR-II-DAP12 receptor recruited the SH2 domain-containing protein tyrosine phosphatase 1 (SHP-1) after BCR stimulation. DAP12-deficient mice showed elevated serum antibodies against self-antigens and enhanced humoral immune responses against T cell-dependent and T cell-independent antigens. Thus, DAP12-coupled MAIR-II negatively regulates B cell-mediated adaptive immune responses.
Assuntos
Imunidade Adaptativa/imunologia , Proteínas Adaptadoras de Transdução de Sinal/imunologia , Linfócitos B/imunologia , Lipodistrofia/imunologia , Osteocondrodisplasias/imunologia , Receptores de Células Matadoras Naturais/imunologia , Proteínas Recombinantes de Fusão/imunologia , Panencefalite Esclerosante Subaguda/imunologia , Proteínas Adaptadoras de Transdução de Sinal/deficiência , Proteínas Adaptadoras de Transdução de Sinal/genética , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Animais , Eletroforese em Gel de Poliacrilamida , Citometria de Fluxo , Vetores Genéticos , Humanos , Lentivirus , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Proteína Tirosina Fosfatase não Receptora Tipo 6/imunologia , Proteína Tirosina Fosfatase não Receptora Tipo 6/metabolismo , Receptores de Células Matadoras Naturais/deficiência , Receptores de Imunoglobulina Polimérica/deficiência , Receptores de Imunoglobulina Polimérica/genética , Receptores de Imunoglobulina Polimérica/imunologia , Receptores de Imunoglobulina Polimérica/metabolismo , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismoRESUMO
Different cellular immune responses are modulated by the cross talk between activating and inhibitory signaling pathways initiated via different cell surface receptors. Similarly, the killing of NK cells is controlled by multiple activating and inhibitory surface receptors. In humans, the major NK triggering receptors, identified so far, include NKp80, 2B4 NKG2D, and CD16 and the natural cytotoxic receptors (collectively named NCRs) include NKp46, NKp44, and NKp30. The two major families of MHC-specific inhibitory receptors identified in humans are the Ig superfamily (KIR and LIR) and the C-type lectin (CD94/NKG2A) receptor superfamily. The different inhibitory receptors show diverse specificity and discriminate between different class I MHC proteins. Much is known about the function and expression patterns of the different NK cell receptors, but the ligand identity of several of the activating NK cell receptors is yet to be discovered. This chapter introduces several research tools that can be used to uncover the identities of different ligands for NK cell receptors.
