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Biomedical subjects

D Cosman

Publications and source records attributed to D Cosman.

At least 19 recordsLinked to original sources
PubMed2001

ULBP1, 2, 3: novel MHC class I-related molecules that bind to human cytomegalovirus glycoprotein UL16, activate NK cells.

New members of the extended MHC class I-like family were identified based on their ability to bind human cytomegalovirus glycoprotein UL16 and/or their mutual homology. Soluble UL16 binding proteins (ULBP) competed with each other for binding to NK cells. Treatment of human and mouse NK cells with ULBP led to increased production of cytokines/chemokines, proliferation, cytotoxic activity and up-regulation of activation-associated surface molecules. The presence of ULBP during the stimulation phase of the CTL assay caused increased cytotoxic activity. Addition of soluble recombinant UL16 protein inhibited the biological activities mediated by ULBP, suggesting the existence of a novel mechanism utilized by CMV to evade elimination by the host immune system.

Animals↗
PubMed2001

ULBPs, novel MHC class I-related molecules, bind to CMV glycoprotein UL16 and stimulate NK cytotoxicity through the NKG2D receptor.

The human cytomegalovirus glycoprotein, UL16, binds to two members of a novel family of molecules, the ULBPs, and to the MHC class I homolog, MICB. The ULBPs are GPI-linked glycoproteins belonging to the extended MHC class I family but are only distantly related to MICB. The ULBP and MICB molecules are ligands for the activating receptor, NKG2D/DAP10, and this interaction is blocked by a soluble form of UL16. The ULBPs stimulate cytokine and chemokine production from NK cells, and expression of ULBPs in NK cell-resistant target cells confers susceptibility to NK cell cytotoxicity. Masking of NK cell recognition of ULBP or MIC antigens by UL16 provides a potential mechanism by which human cytomegalovirus-infected cells might evade attack by the immune system.

Amino Acid Sequence↗
PubMed2001

The UL16-binding proteins, a novel family of MHC class I-related ligands for NKG2D, activate natural killer cell functions.

The UL16-binding proteins (ULBPs) are a novel family of MHC class I-related molecules (MICs) that were identified based on their ability to bind to the human cytomegalovirus (HCMV) glycoprotein UL16. UL16 also binds to a member of another family of MHC class I-like molecules, MICB. The ULBPs and MICs are ligands for NKG2D/DAP10, an activating receptor expressed by natural killer (NK) cells and other immune effector cells, and this interaction can be blocked by UL16. Engagement of NKG2D/DAP10 by ULBPs or MICs expressed on a target cell can overcome an inhibitory signal generated by NK-cell recognition of MHC class I molecules and trigger NK cytotoxicity. ULBPs elicit their effects on NK cells by activating the janus kinase 2, signal transducer and activator of transcription 5, extracellular-signal-regulated kinase mitogen-activated protein kinase and Akt/protein kinase B signal transduction pathways. Although ULBPs alone activate multiple signaling pathways and induce modest cytokine production, ULBPs synergize strongly with interleukin-12 for production of interferon-gamma by NK cells. This finding is consistent with reports in T cells that NKG2D/DAP10 can act as a co-stimulatory receptor in a similar manner as CD28. The possible roles of ULBPs in mediating immune responses to viruses and tumors and the potential mechanisms by which UL16 may allow HCMV to evade immune detection are areas of active investigation.

Animals↗
PubMed2000

The CD85/LIR-1/ILT2 inhibitory receptor is expressed by all human T lymphocytes and down-regulates their functions.

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.

Antibodies, Monoclonal↗
PubMed2000

LIRs/ILTs/MIRs, inhibitory and stimulatory Ig-superfamily receptors expressed in myeloid and lymphoid cells.

Cells exhibit a complex network of inhibitory and stimulatory signaling pathways, which interact with each other to maintain an homeostatic balance and modulate cellular responses to external stimuli. During most of the 1980s, a great effort was put into the characterization of stimulatory cell surface receptors for cytokines and growth factors. In the last decade, a large number of inhibitory receptors have been identified and it has become apparent that inhibitory signaling pathways are subject to intricate regulatory mechanisms. Inhibitory and stimulatory signaling pathways work in concert with each other to establish activation thresholds and provide sensitive tuning mechanisms that help control cellular responses. LIRs/ILTs/MIRs are a novel family of inhibitory and stimulatory receptors expressed both in myeloid and lymphoid cells. They contain two or four immunoglobulin-like domains in the extracellular region and their cytoplasmic domains are either very short and without any signaling motifs or are long and contain a variable number of immunoreceptor tyrosine-based inhibition motifs (ITIMs). LIRs within the first group send stimulatory signals by association with the FcR common gamma chain and LIRs within the second group deliver inhibitory signals by association with the protein tyrosine phosphatase SHP-1. This review summarizes our current knowledge on the LIRs, their ligands, and biological functions.

Amino Acid Motifs↗
PubMed1999

RANK is essential for osteoclast and lymph node development.

The physiological role of the TNF receptor (TNFR) family member, RANK, was investigated by generating RANK-deficient mice. RANK(-/-) mice were characterized by profound osteopetrosis resulting from an apparent block in osteoclast differentiation. RANK expression was not required for the commitment, differentiation, and functional maturation of macrophages and dendritic cells from their myeloid precursors but provided a necessary and specific signal for the differentiation of myeloid-derived osteoclasts. RANK(-/-) mice also exhibited a marked deficiency of B cells in the spleen. RANK(-/-) mice retained mucosal-associated lymphoid tissues including Peyer's patches but completely lacked all other peripheral lymph nodes, highlighting an additional major role for RANK in lymph node formation. These experiments reveal that RANK provides critical signals necessary for lymph node organogenesis and osteoclast differentiation.

Animals↗
PubMed1999

IFN-gamma mediates a novel antiviral activity through dynamic modulation of TRAIL and TRAIL receptor expression.

TNF-related apoptosis-inducing ligand (TRAIL) is able to kill many transformed cells of diverse tissue types. We show that TRAIL is inducible by IFN-gamma, by TNF-alpha, and by infection with human CMV, and has potent antiviral activity in vitro. CMV infection and IFN-gamma also reciprocally modulate TRAIL receptor (TRAIL-R) expression. CMV infection increased the expression of TRAIL-R1 and -R2, whereas IFN-gamma down-regulated the expression of TRAIL-Rs on uninfected fibroblasts. Moreover, IFN-gamma significantly decreased the basal level of NF-kappaB activation, a known survival factor that inhibits apoptosis. Thus, TRAIL selectively kills virus-infected cells while leaving uninfected cells intact, and IFN-gamma potentiates these effects by dynamic modulation of TRAIL and TRAIL-R expression and by sensitizing cells to apoptosis. The regulation of TRAIL and TRAIL-R expression may represent a general mechanism that contributes to the control of TRAIL-mediated apoptosis.

Adjuvants, Immunologic↗
PubMed1999

Functional role of interleukin-4 (IL-4) and IL-7 in the development of X-linked severe combined immunodeficiency.

X-linked severe combined immunodeficiency (X-SCID) is characterized by an absent or diminished number of T cells and natural-killer (NK) cells with a normal or elevated number of B cells, and results from mutations of the gammac chain. The gammac chain is shared by interleukin-2 (IL-2), IL-4, IL-7, IL-9, and IL-15 receptors. Recently, a survival signal through the IL-7 receptor alpha (IL-7Ralpha) chain was shown to be important for T-cell development in mice and was suggested to contribute to the X-SCID phenotype. In the present study, we examined function of a mutant gammac chain (A156V) isolated from an X-SCID patient and found that T cells expressing the mutant gammac chain were selectively impaired in their responses to IL-4 or IL-7 compared with the wild-type gammac chain expressing cells although responses to IL-2 or IL-15 were relatively maintained. The result shows that IL-4- and/or IL-7-induced signaling through the gammac chain is critical for T-cell development and plays an important role in the development of the X-SCID phenotype.

Genetic Linkage↗
PubMed1999

The leukocyte immunoglobulin-like receptors (LIRs): a new family of immune regulators.

Identification of a counterstructure for the human cytomegalovirus-encoded major histocompatibility complex class I-related gene product, UL18, has led to the discovery of a novel family of immunoreceptors, termed leukocyte immunoglobulin-like receptors (LIRs). The LIRs are differentially expressed in cells of the dendritic cell, monocytic and lymphocytic lineages, and appear to mediate diverse roles in immune regulation. This review summarizes the expression, distribution, and signaling capacities of the LIRs and discusses possible roles of the LIRs in both inhibition and activation of the cellular responses.

Animals↗
PubMed1999

A novel mutant gammac chain from a patient with typical phenotype of X-linked severe combined immunodeficiency (SCID) has partial signalling function for mediating IL-2 and IL-4 receptor action.

Mutations of the common gamma (gammac) chain result in X-linked SCID (X-SCID), which is characterized by the reduction in number or absence of peripheral blood T cells and natural killer (NK) cells, with retention of normal numbers of B cells. In the present study we describe a novel mutant gammac chain of an X-SCID patient with a typical X-SCID phenotype. This mutant receptor subunit is able to associate with Jak3 to transduce a weak signal. The Jak3-specific action is demonstrated by the induction of gene expression through the haematopoietin receptor response element (HRRE) by IL-2 and IL-4 in the experimental model of transiently transfected hepatoma cells over-expressing Jak3. This result suggests that a threshold in the gammac-Jak3 interaction determines the X-SCID phenotype.

Genetic Linkage↗
PubMed1999

The leukocyte Ig-like receptor (LIR)-1 for the cytomegalovirus UL18 protein displays a broad specificity for different HLA class I alleles: analysis of LIR-1 + NK cell clones.

Leukocyte Ig-like receptor (LIR)-1 is a member of the Ig superfamily which has been shown to bind the human cytomegalovirus MHC class I homologue UL-18 protein. In this study, we have analyzed the expression and function of LIR-1 in human NK cells. We show that LIR-1 is expressed by a subset of NK cells variable in size among different donors. When compared to the known HLA class I-specific NK receptors, the expression of LIR-1 was found to be partially overlapped with that of CD94-NKG2A or with that of killer inhibitory receptors (KIR) belonging to the Ig superfamily. The use of the soluble form of UL-18 molecule revealed, in double fluorescence analysis, a selective binding to LIR-1 + cells while no correlation was observed between expression of either KIR or CD94-NKG2A molecules and ability to bind UL18. We further determined whether LIR-1 could also function as receptor for HLA class I molecules. To this end, we assessed the capability of LIR-1 + NK cell clones of lysing HLA class I- target cells transfected with different class I alleles, including HLA-A, -B, -C and -G alleles. Data revealed that LIR-1 functions as a broad HLA class I-specific inhibitory receptor recognizing different alleles coded for by different HLA loci.

Alleles↗
PubMed1999

The R27080 glycoprotein is abundantly secreted from human cytomegalovirus-infected fibroblasts.

A 45 kDa glycoprotein was purified from the culture media of human cytomegalovirus (HCMV)-infected fibroblasts. N-terminal sequencing revealed that the protein, R27080, is the translation product of the R27080 open reading frame of HCMV. R27080 is highly glycosylated and contains no cysteine or methionine residues. Proteolytic cleavage of R27080 by a furin-like enzyme was analysed in transfected COS-7 cells. R27080 is the first identified viral protein secreted from HCMV-infected cells.

Amino Acid Sequence↗
PubMed1999

Human cytomegalovirus, MHC class I and inhibitory signalling receptors: more questions than answers.

The human cytomegalovirus UL18 protein, an MHC class I homologue, has been shown to bind to leucocyte immunoglobulin-like receptor (LIR)-1, a member of a family of nine closely related immunoglobulin superfamily receptors expressed on leucocytes. The LIRs are related to the natural killer (NK)-cell immunoglobulin-like receptors and to several other immunoreceptors. Three groups of LIR molecules have been defined: those containing cytoplasmic domain inhibitory signalling motifs, those with short cytoplasmic domains and a charged residue within the transmembrane domain, and a secreted molecule. LIR-1 and LIR-2 bind to a broad spectrum of cellular MHC class I antigens, including HLA-A, -B and -C alleles. LIR-2 is expressed by all monocytes and dendritic cells, whereas LIR-1 is additionally expressed by B cells and subsets of T and NK cells. Upon tyrosine phosphorylation, LIR-1 and LIR-2 associate with the tyrosine phosphatase, SHP-1, and have been shown to inhibit Fc gamma RI signalling when co-crosslinked in monocytes. Evidence for and against a role of UL18 as an inhibitor of NK-cell function is discussed, as are possible functional outcomes of UL18-LIR-1 interactions in monocytic cells.

Animals↗
PubMed1998

The involvement of multiple tumor necrosis factor receptor (TNFR)-associated factors in the signaling mechanisms of receptor activator of NF-kappaB, a member of the TNFR superfamily.

Receptor activator of NF-kappaB (RANK) is a recently identified member of the tumor necrosis factor receptor superfamily and is expressed on activated T cells and dendritic cells. Its cognate ligand (RANKL) plays significant roles in the activation of dendritic cell function and osteoclast differentiation. We demonstrate here the interaction of RANK with tumor necrosis factor receptor-associated factors (TRAFs) 1, 2, 3, 5, and 6 both in vitro and in cells. Mapping of the structural requirements for TRAF/RANK interaction revealed multiple TRAF binding sites clustered in two distinct domains in the RANK cytoplasmic tail. These TRAF binding domains were shown to be functionally important for the RANK-dependent induction of NF-kappaB and c-Jun NH2-terminal kinase activities. Site-directed mutagenesis demonstrated that these TRAF binding sites exhibited selective binding for different TRAF proteins. In particular, TRAF6 interacted with membrane-proximal determinants distinct from those binding TRAFs 1, 2, 3, and 5. When this membrane-proximal TRAF6 interaction domain was deleted, RANK-mediated NF-kappaB signaling was completely inhibited while c-Jun NH2-terminal kinase activation was partially inhibited. An NH2-terminal truncation mutant of TRAF6 inhibited RANKL-mediated NF-kappaB activation, but failed to affect constitutive signaling induced by receptor overexpression, revealing a selective role for TRAF6 in ligand-induced activation events.

Binding Sites↗
PubMed1998

The MHC class I binding proteins LIR-1 and LIR-2 inhibit Fc receptor-mediated signaling in monocytes.

The MHC class I binding proteins leukocyte immunoglobulin-like receptor (LIR)-1 and -2 recognize a similar broad spectrum of HLA-A, -B and -C alleles but are differentially expressed in lymphocytes, monocytes, and dendritic cells. In monocytes, phosphorylation of LIR-1 and LIR-2 results in the binding of the tyrosine phosphatase SHP-1. Coligation of either LIR with Fcgamma receptor I (CD64) inhibits tyrosine phosphorylation of the associated Fc receptor gamma chain and Syk molecules, as well as intracellular calcium mobilization. These findings suggest that LIR-1 and LIR-2 function as unique MHC class I receptors involved in the inhibition or down-modulation of monocyte activation signals, particularly those mediated through the receptors for IgG, IgE and IgA.

Alleles↗
PubMed1997

A family of human lymphoid and myeloid Ig-like receptors, some of which bind to MHC class I molecules.

Leukocyte Ig-like receptors (LIRs) are a newly discovered family of immunoreceptors expressed on monocytes and B cells and at lower levels on dendritic cells and NK cells. The amino acid sequences in the extracellular regions of eight of these receptors show between 63 and 84% identity to the prototypic LIR-1 sequence. LIRs contain either two or four Ig domains and fall into three classes: those with cytoplasmic domains containing two, three, or four immunoreceptor tyrosine-based inhibitory motif-like motifs; those with a short cytoplasmic domain and no immunoreceptor tyrosine-based inhibitory motif-like motifs; and those with no transmembrane domain represented by a single LIR molecule that is presumably secreted. The LIRs are structurally related to the human Fc(alpha)R and the killer inhibitory receptors and map to the same region of chromosome 19 as these genes. Like killer inhibitory receptors, at least two LIRs bind to MHC class I Ags, but their different cellular distribution suggests a distinct role in immune system modulation.

Amino Acid Sequence↗