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Olivia M Martinez

Publications and source records attributed to Olivia M Martinez.

14 recordsLinked to original sources
PubMed2007

Epstein-Barr virus: evasive maneuvers in the development of PTLD.

Epstein-Barr virus (EBV) infection is linked to approximately 90% of B-cell lymphomas associated with posttransplant lymphoproliferative disease (PTLD), a serious complication for immunosuppressed transplant recipients. In this paper, we review the myriad ways by which EBV can inadvertently drive the genesis and persistence of B-cell lymphomas, particularly when the antiviral immune response is compromised. Probing the basic mechanisms by which EBV infection proceeds and contributes to malignancy in such cases will hopefully improve our understanding and treatment of PTLD and other EBV-associated malignancies.

Epstein-Barr Virus Infections↗
PubMed2006

EBV can protect latently infected B cell lymphomas from death receptor-induced apoptosis.

The relationship between EBV infection and sensitivity to death receptor (DR)-induced apoptosis is poorly understood. Using EBV- and EBV+ BJAB cells, we provide the first evidence that EBV can protect latently infected B cell lymphomas from apoptosis triggered through Fas or TRAIL receptors. Caspase 8 activation was impaired and cellular FLIP recruitment was enriched in death-inducing signaling complexes formed in EBV-infected BJAB cells relative to parent BJAB cells. Furthermore, latent membrane protein 1 expression alone could reduce caspase activation and confer partial resistance to DR apoptosis in BJAB cells. This protective effect was dependent on C-terminal activating region 2-driven NF-kappaB activation, which in turn up-regulated cellular FLIP expression in latent membrane protein 1+ BJAB cells. Thus, the ability of latent EBV to block DR apoptosis may help to ensure the survival of host cells during B cell differentiation, and contribute to the development of B cell lymphomas, especially in immunocompromised individuals.

Apoptosis↗
PubMed2006

CD72 down-modulates BCR-induced signal transduction and diminishes survival in primary mature B lymphocytes.

CD72, a 45-kDa type II transmembrane glycoprotein carrying an ITIM motif, is believed to be an inhibitory coreceptor of the BCR. Mature B cells lacking CD72 show enhanced Ca(2+) mobilization and are hyperproliferative in response to BCR ligation. However, the signal transduction pathways downstream of BCR signaling that transmit the inhibitory effect of CD72 in mature B cells remain unknown. To address this question, we used hen egg lysozyme-specific BCR transgenic mice to elucidate the differential cell signaling between wild-type and CD72-deficient B cells in response to hen egg lysozyme Ag stimulation. Our results demonstrate that CD72 predominantly down-regulates the major signal transduction pathways downstream of the BCR, including NF-AT, NF-kappaB, ERK, JNK, p38-MAPK, and PI3K/Akt in mature B cells. CD72 ligation with anti-CD72 Ab (K10.6), which mimics the binding of CD100 (a natural ligand for CD72) to release the inhibitory function of CD72, augments cell proliferation, Ca(2+) flux, IkappaBalpha activation, and ERK MAPK activity upon Ag stimulation in wild-type B cells. In addition, we show direct evidence that CD72 promotes cell cycle arrest and apoptosis after Ag stimulation in mature B cells. Taken together, our findings conclude that CD72 plays a dominant role as a negative regulator of BCR signaling in primary mature B lymphocytes.

Animals↗
PubMed2006

NKp30 is a functional activation receptor on a subset of rat natural killer cells.

NKp30 is a stimulatory receptor on human NK cells implicated in tumor immunity, and is capable of promoting or terminating dendritic cell maturation. To gain a better understanding of NKp30 biology, we have investigated the expression and function of rat NKp30 (rNKp30). We generated stable transfectants of rNKp30 in RNK16 cells, a rat NK lymphoma line, and used a novel panel of mAb against rNKp30 to study this receptor. Using agonistic rNKp30 mAb, we demonstrated that rNKp30 mediates robust IFN-gamma production and cytolytic responses from rNKp30-transfected RNK16 cells. We determined by flow cytometry that rNKp30 is expressed by a subset of primary NK cells isolated from the blood and spleen, and to a lesser extent also on liver NK cells. Stimulation of rNKp30 on primary NK cells led to IFN-gamma production. Liver NK cells expressed low levels of NKp30 and had reduced rNKp30-mediated IFN-gamma responses. During an alloimmune response in vivo, the proportion of the rNKp30(+) NK cell subset in the peripheral blood significantly increased, suggesting that rNKp30 may play an important role during alloactivation. Thus, our data demonstrate that NKp30 is indeed expressed in rodents and is a functional stimulatory receptor in a subset of rat NK cells.

Animals↗
PubMed2006

Reproduction and pregnancy in transplant recipients: current practices.

Many transplant physicians are faced with questions from their patients about the safety and long-term consequences of pregnancy following transplantation. To better understand how pregnancies are managed and to clarify the outcome of pregnancy after transplantation, a survey questionnaire was developed and mailed to all medical and surgical directors of transplant centers throughout the United States; responses were obtained from 59.1% of the transplant centers. Although many opinions were collected, most respondents conceded that their opinions were based on personal experience rather than evidence-based. The underutilization of existing information was revealing and highlighted a need for an evidence-based approach to care of the pregnant transplant recipient and her offspring. The survey results, reported in this article, led to formation of a consensus conference to determine the optimal approach to pregnant transplant recipients and to define what is currently known and unknown about reproduction and transplantation.

Contraceptives, Oral↗
PubMed2005

Reproduction and transplantation: report on the AST Consensus Conference on Reproductive Issues and Transplantation.

It has been almost 50 years since the first child was born to a female transplant recipient. Since that time pregnancy has become common after transplantation, but physicians have been left to rely on case reports, small series and data from voluntary registries to guide the care of their patients. Many uncertainties exist including the risks that pregnancy presents to the graft, the patient herself, and the long-term risks to the fetus. It is also unclear how to best modify immunosuppressive agents or treat rejection during pregnancy, especially in light of newer agents available where pregnancy safety has not been established. To begin to address uncertainties and define clinical practice guidelines for the transplant physician and obstetrical caregivers, a consensus conference was held in Bethesda, Md. The conferees summarized both what is known and important gaps in our knowledge. They also identified key areas of agreement, and posed a number of critical questions, the resolution of which is necessary in order to establish evidence-based guidelines. The manuscript summarizes the deliberations and conclusions of the conference as well as specific recommendations based on current knowledge in the field.

Female↗
PubMed2005

IFN-gamma, produced by NK cells that infiltrate liver allografts early after transplantation, links the innate and adaptive immune responses.

The role of NK cells following solid organ transplantation remains unclear. We examined NK cells in acute allograft rejection using a high responder model (DA-->Lewis) of rat orthotopic liver transplantation. Recipient-derived NK cells infiltrated liver allografts early after transplantation. Since chemokines are important in the trafficking of cells to areas of inflammation, we determined the intragraft expression of chemokines known to attract NK cells. CCL3 was significantly increased in allografts at 6 h post-transplant as compared to syngeneic grafts whereas CCL2 and CXCL10 were elevated in both syngeneic and allogeneic grafts. CXCL10 and CX3CL1 were significantly upregulated in allografts by day 3 post-transplant as compared to syngeneic grafts suggesting a role for these chemokines in the recruitment of effector cells to allografts. Graft-infiltrating NK cells were shown to be a major source of IFN-gamma, and IFN-gamma levels in the serum were markedly increased, specifically in allograft recipients, by day 3 post-transplant. Accordingly, in the absence of NK cells the levels of IFN-gamma were significantly decreased. Furthermore, graft survival was significantly prolonged. These data suggest that IFN-gamma-producing NK cells are an important link between the innate and adaptive immune responses early after transplantation.

Animals↗
PubMed2004

Identification, cloning, and characterization of a novel rat natural killer receptor, RNKP30: a molecule expressed in liver allografts.

BACKGROUND: As a component of the innate immune system, natural killer (NK) cells may play a significant role in the early events after solid-organ transplantation. Activated NK cells have been shown to infiltrate allografts in transplant models. To better understand NK cells and the role of NK cell receptors in transplantation, we have cloned and begun characterizing a novel rat molecule, rNKp30. METHODS: RNKp30 cDNA was cloned by 5' rapid amplification of cDNA ends polymerase chain reaction (PCR) and reverse transcriptase (RT)-PCR from mononuclear cells infiltrating a rejecting liver allograft. Southern blot analysis was used to determine the rNKp30 gene copy number. RT-PCR and Northern blotting were used to examine rNKp30 RNA expression in NK cells, multiple tissues, and liver grafts. Immunocytochemistry, immunoprecipitation, and Western blot analysis with two anti-rNKp30 polyclonal antibodies, CA680 and CA1071, were performed. Tunicamycin and endoglycosidase treatments determined the extent of rNKp30 glycosylation. RESULTS: RNKp30 is homologous to human and macaque NKp30. It is a single copy gene with five identified single-nucleotide polymorphisms. RNKp30 is expressed by NK cells and is detectable as a single transcript by Northern blot in normal spleen, lymph node, and lung tissues. RNKp30 is a variably N-glycosylated cell surface molecule with a protein backbone of approximately 21 kDa. Elevated transcript expression of rNKp30 is detected in both rejected and spontaneously accepted liver allografts, but not in syngeneic or cyclosporine A-treated allografts. CONCLUSIONS: RNKp30 is a glycosylated surface NK cell receptor with limited polymorphism. This putative activation receptor is expressed in liver allografts and may participate in the innate immune response after transplantation.

Amino Acid Sequence↗
PubMed2003

Rapamycin inhibits the interleukin 10 signal transduction pathway and the growth of Epstein Barr virus B-cell lymphomas.

EBV-infected B-cell lymphomas are a potentially life-threatening complication in bone marrow and solid organ transplant recipients. Immunosuppressive drugs required to prevent allograft rejection also impair anti-EBV T-cell immunity, thereby increasing the risk of EBV-associated disease. Here we demonstrate that the immunosuppressant rapamycin (RAPA) has a strong antiproliferative effect in vitro on B-cell lines derived from organ transplant recipients with EBV-associated posttransplant lymphoproliferative disorder (PTLD). Furthermore, RAPA significantly inhibits or delays the growth of solid tumors established from EBV-infected B-cell lines in a xenogeneic mouse model of PTLD. RAPA acts via cell cycle arrest, induction of apoptosis, and, most importantly, inhibition of interleukin 10 secretion, a necessary autocrine growth factor. The reduced interleukin 10 production is accompanied by corresponding decreases in the constitutive activation of the growth-promoting transcription factors signal transducer and activator of transcription 1 and 3. Thus, RAPA can limit B-cell lymphoma growth while simultaneously providing immunosuppression to prevent graft rejection in patients who are otherwise at risk for EBV-associated PTLD. Moreover, these findings may have application to other EBV-associated malignancies.

Animals↗
PubMed2002

Identification of Epstein-Barr virus-specific CD8+ T lymphocytes in the circulation of pediatric transplant recipients.

BACKGROUND: Pediatric transplant recipients are at increased risk for Epstein Barr virus (EBV)-related B cell lymphomas. In healthy individuals, the expansion of EBV-infected B cells is controlled by CD8+ cytotoxic T cells. However, immunosuppressive therapy may compromise antiviral immunity. We identified and determined the frequency of EBV-specific T cells in the peripheral blood of pediatric transplant recipients. METHODS: HLA-B*0801 and HLA-A*0201 tetramers folded with immunodominant EBV peptides were used to detect EBV-specific CD8+ T cells by flow cytometry in peripheral blood mononuclear cells from 24 pediatric liver and kidney transplant recipients. The expression of CD38 and CD45RO on EBV-specific, tetramer-binding cells was also examined in a subset of patients by immunofluorescent staining and flow cytometry. RESULTS: Tetramer-binding CD8+ T cells were identified in 21 of 24 transplant recipients. EBV-specific CD8+ T cells were detected as early as 4 weeks after transplant in EBV seronegative patients receiving an organ from an EBV seropositive donor. The frequencies (expressed as a percentage of the CD8+ T cells) of the tetramer-binding cells were HLA-B8-RAKFKQLL (BZLF1 lytic antigen peptide) tetramer, range=0.96 to 3.94%; HLA-B8-FLRGRAYGL (EBNA3A latent antigen peptide) tetramer, range=0.03 to 0.59%; and HLA-A2-GLCTLVAML (BMLF1 lytic antigen peptide) tetramer, range=0.06 to 0.76%. The majority of tetramer reactive cells displayed an activated/memory phenotype. CONCLUSIONS: Pediatric transplant recipients receiving immunosuppression can generate EBV-specific CD8+ T cells. Phenotypic and functional analysis of tetramer cells may prove useful in defining and monitoring EBV infection in the posttransplant patient.

ADP-ribosyl Cyclase↗
PubMed2002

Constitutive activation of Jak/STAT proteins in Epstein-Barr virus-infected B-cell lines from patients with posttransplant lymphoproliferative disorder.

BACKGROUND: Posttransplant lymphoproliferative disease (PTLD) is a major complication after bone marrow and solid organ transplantation. The disease encompasses a spectrum of abnormal, Epstein-Barr virus (EBV)-associated B-cell proliferations. We have previously shown that EBV-infected, spontaneous lymphoblastoid cell lines (SLCL) derived from PTLD patients require autocrine interleukin (IL)-10 to proliferate. To determine if cytokine signal transduction is involved in the autonomous growth of the SLCL, the activation states of the Jak/STAT signaling pathway proteins were analyzed in three different SLCL, termed JB7, MF4, and VB4. METHODS: The tyrosine phosphorylation (P-tyr) states of the Janus kinases (Jaks) and signal transducers and activators of transcription (STAT) proteins were examined by immunoprecipitation and immunoblot. Activated STAT dimer formation was determined by electromobility shift assays. RESULTS: All three SLCL, but not the Daudi Burkitt's lymphoma B-cell line, expressed the four known Jak kinases constitutively tyrosine phosphorylated, with particularly high levels of P-tyr Jak1 in the JB7 line. STAT1 and STAT3, but not STAT2 or STAT5, are also constitutively activated in all SLCL. The ability of the activated STAT proteins to form DNA-binding dimers was confirmed by electromobility shift assay. The SLCL, but not the Daudi line, express activated STAT complexes composed of STAT1 and STAT3. Another EBV-infected B-cell line, isolated from a lymph node biopsy after kidney transplantation, is phenotypically similar to the other SLCL in both surface antigen and activated STAT1 and STAT3 expression. CONCLUSION: These data support the presence of a constitutively active autocrine signaling pathway consistent with IL-10 in the SLCL.

Antigens, CD↗
PubMed2002

CD30 expression identifies the predominant proliferating T lymphocyte population in human alloimmune responses.

CD30 is an inducible member of the TNFR superfamily that is expressed on activated T and B cells and some lymphoid malignancies. We have previously shown that human CD30(+) T cells elicited with allogeneic APC are a major source of IFN-gamma and IL-5 production. In the present study we have used alloantigen, as well as anti-CD3 plus anti-CD28 mAb stimulation, to further characterize human CD30(+) T cells with respect to function and the expression of other activation-dependent cell surface molecules, including the related TNFR family members OX-40 and 4-1BB (CD137). Our results indicate that human CD30(+) T cells are a subset of activated T cells that also express CD25 and CD45RO. Moreover, we observed that allogeneic APC consistently induced a greater proportion of CD30(+) cells within the activated T cell population than did stimulation with plate-bound anti-CD3 plus anti-CD28 mAb or stimulation with soluble anti-CD3 plus anti-CD28 and autologous APC. The enhanced induction of CD30 expression by alloantigen was not common to other inducible TNFR family members because anti-CD3 plus anti-CD28 mAbs were far more effective in inducing expression of 4-1BB and OX-40. Furthermore, CD30 expression marked the predominant proliferating T cell population induced by alloantigen as determined by CFSE staining and flow cytometry. These results indicate that CD30, but not 4-1BB or OX-40, is preferentially induced by alloantigen, suggesting that CD30 may be important in human alloimmune responses.

Antigen-Presenting Cells↗
PubMed2002

NK cells and transplantation.

The requirement for cytotoxic T lymphocytes during allograft rejection is controversial. We have demonstrated that CD8+ T cells are not essential for allograft rejection or for the induction of apoptosis in two experimental models of transplantation. To determine candidate cells types which may play a role in the events leading to graft rejection, the cellular composition of rejecting allografts was determined. We demonstrate that substantial numbers of NK cells, of recipient origin, infiltrate allografts as early as 12 h after transplantation. These NK cells produce cytokines and express cytotoxic mediators such as granzyme B and FasL. It is unknown which NK cell receptors are expressed and activated during transplantation. NK cells express multiple cell surface receptors, including MHC class I binding inhibitory receptors, which deliver a negative signal, and activation receptors, which stimulate cytokine secretion and cytotoxicity of NK cells. To begin to understand NK cell activation in the context of transplantation, we have recently cloned a novel rat immunoglobulin-like surface receptor from a rejecting liver allograft. Sequence analysis demonstrates that this putative activation receptor contains 71% identity to human NKp30 at the DNA level, suggesting that it is the rat homologue (rNKp30). Characterization of NK activation receptors may lead to better understanding of the interactions between the innate and adaptive immune responses in transplantation.

Animals↗