Purification and characterization of a pregnancy-associated protein: TJ6s

Breast cancer associated a2 isoform vacuolar ATPase immunomodulates neutrophils: potential role in tumor progression

In invasive breast cancer, tumor associated neutrophils (TAN) represent a significant portion of the tumor mass and are associated with increased angiogenesis and metastasis. Identifying the regulatory factors that control TAN behavior will help in developing ideal immunotherapies. Vacuolar ATPases (V-ATPases), multi-subunit proton pumps, are highly expressed in metastatic breast cancer cells. A cleaved peptide from a2 isoform V-ATPase (a2NTD) has immunomodulatory role in tumor microenvironment. Here, we report for the first time the role of V-ATPase in neutrophils modulation. In invasive breast cancer cells, a2NTD was detected and a2V was highly expressed on the surface. Immunohistochemical analysis of invasive breast cancer tissues revealed that increased neutrophil recruitment and blood vessel density correlated with increased a2NTD levels. In order to determine the direct regulatory role of a2NTD on neutrophils, recombinant a2NTD was used for the treatment of neutrophils isolated from the peripheral blood of healthy volunteers. Neutrophils treated with a2NTD (a2Neuɸ) showed increased secretion of IL-1RA, IL-10, CCL-2 and IL-6 that are important mediators in cancer related inflammation. Moreover, a2Neuɸ exhibited an increased production of protumorigenic factors including IL-8, matrix metaloprotinase-9 and vascular endothelial growth factor. Further, functional characterization of a2Neuɸ revealed that a2Neuɸ derived products induce in vitro angiogenesis as well as increase the invasiveness of breast cancer cells. This study establishes the modulatory effect of breast cancer associated a2V on neutrophils, by the action of a2NTD, which has a positive impact on tumor progression, supporting that a2V can be a potential selective target for breast cancer therapy.

Regeneration and Tolerance Factor: A Novel Mediator of Glioblastoma-Associated Immunosuppression

Regeneration and tolerance factor (RTF) was originally identified in placenta where it is thought to be essential for fetal allograft survival. Here we report that RTF mRNA and protein are also expressed in human glioma cells in vitro and in vivo. Suppression of RTF expression by RNA interference promotes the lysis of glioma cells by natural killer (NK) and T cells in vitro. Moreover, RTF-depleted glioma cells are less tumorigenic than control cells in nude mice in vivo. Depletion of NK cells in these animals abolished this effect. RTF is thus a novel aberrantly expressed molecule which confers immune privilege to human malignant gliomas.

Cloning, expression and functional characterization of the putative regeneration and tolerance factor (RTF/TJ6) as a functional vacuolar ATPase proton pump regulatory subunit with a conserved sequence of immunoreceptor tyrosine-based activation motif

In an attempt to identify new immunoreceptor tyrosine-based activation motif (ITAM)-containing human molecules that may regulate hitherto unknown immune cell functions, we BLAST searched the National Center for Biotechnology Information database for ITAM-containing sequences. A human expressed sequence tag showing partial homology to the murine TJ6 (mTJ6) gene and encoding a putative ITAM sequence has been identified and used to clone the human TJ6 (hTJ6) gene from an HL-60-derived cDNA library. hTJ6 was found to encode a protein of 856 residues with a calculated mass of 98 155 Da. Immunolocalization and sequence analysis revealed that hTJ6 is a membrane protein with predicted six transmembrane-spanning regions, typical of ion channels, and a single putative ITAM (residues 452-466) in a juxtamembrane or hydrophobic intramembrane region. hTJ6 is highly homologous to Bos taurus 116-kDa subunit of the vacuolar proton-translocating ATPase. Over-expression of hTJ6 in HEK 293 cells increased H+ uptake into intracellular organelles, an effect that was sensitive to inhibition by bafilomycin, a selective inhibitor of vacuolar H+ pump. Northern blot analysis demonstrated three different hybridizing mRNA transcripts corresponding to 3.2, 5.0 and 7.3 kb, indicating the presence of several splice variants. Significant differences in hTJ6 mRNA levels in human tissues of different origins point to possible tissue-specific function. Although hTJ6 was found to be a poor substrate for tyrosine-phosphorylating enzymes, suggesting that its ITAM sequence is non-functional in protein tyrosine kinase-mediated signaling pathways, its role in organellar H+ pumping suggests that hTJ6 function may participate in protein trafficking/processing.

The Placental Immunomodulatory Cytokine Regeneration and Tolerance Factor is also Expressed by Both Human Cycling and Early Pregnant Endometrium

PROBLEM

Regeneration and tolerance factor (RTF) has been recently suggested to contribute to the control of fetal-ablating immunity at the maternal-fetal interface through the induction of T helper 2 (Th2)-dominated response. The protein consists of a membrane-associated domain and an extracellular portion which is proteolitically cleaved to yield a soluble peptide. In humans, it has been shown to be expressed by invading cytotrophoblasts and decidual lymphoid cells, to be increased on peripheral blood B lymphocytes during a normal gestation and on circulating natural killer cells during unsuccessful pregnancies. However, the expression of RTF in other cell types and, specifically, in non-hematopoietic maternal cells of the human uterus has not been characterized in detail. Thus, we have specifically studied the expression and modulation of the cytokine in human endometrium obtained in different phases of the cycle and in early pregnancy.

METHODS

The 20 kDa extracellular domain of RTF has been localized by immunohistochemical method and Western blot analysis. Levels of RTF messenger RNA (mRNA) in basal and stimulated conditions have been evaluated by semiquantitative reverse transcription-polymerase chain reaction.

RESULTS

The extracellular domain of RTF could be detected in both the glandular epithelium and stroma with diffuse distribution in both cycling endometrium and first trimester decidua. Both cycling and pregnant endometrium expressed the gene for RTF but mRNA levels resulted significantly increased in secretory phase-endometrial stromal cells when compared to proliferative phase samples. Inflammatory cytokines, interleukin-1beta and tumour necrosis factor alpha were able to directly increase endometrial RTF mRNA expression.

CONCLUSION

These results indicate that RTF is constitutively expressed at endometrial and decidual level and its up-regulation during the secretory phase of the cycle may be relevant in mediating some immune-related aspects of uterine physiology.

PLIF induces IL-10 production in monocytes: a calmodulin-p38 mitogen-activated protein kinase-dependent pathway

Recently, we reported the cloning and preliminary characterization of a novel human immunomodulator named PLIF (placenta immunomodulatory ferritin). PLIF has a unique molecular structure, which is composed of a ferritin heavy chain-like domain and a novel cytokine-like domain called C48. Both intact molecule and C48 inhibit T cell proliferation following allogeneic or anti-CD3 stimuli. PLIF is localized at the fetal-maternal interface of human placenta and might play a role in down-modulating the maternal immune reaction toward the embryo. The inhibitory effect of PLIF on T cell activation can be direct, indirect through cytokine mediators, or both. In the present study we investigated the possible indirect effects of PLIF by using its bioactive domain C48. Measurement of various cytokines revealed that C48, predominantly, induce pronounced and rapid IL-10 production in monocytes, which is immune activation-independent. Further, we discovered that C48-induced IL-10 production is mediated through a calcium/calmodulin-p38 mitogen-activated protein (MAP) kinase signaling pathway. However, extracellular signal-related kinases1,2 (ERK1,2), also activated by C48 stimulation, exhibited a limiting effect on IL-10 production.

Expression of regeneration and tolerance factor correlates directly with human immunodeficiency virus infection and inversely with hepatitis C virus infection

Hepatitis C virus (HCV) and human immunodeficiency virus (HIV) cause two of the most prevalent debilitating viral infections. HIV appears to induce a skewing toward a Th2 response, while in HCV infection a Th1 response appears to dominate. Regeneration and tolerance factor (RTF) may participate in driving or sustaining a Th2 cytokine response. The expression of RTF on CD3(+) T cells of HIV-seropositive (HIV(+)) individuals is increased. The purpose of this study was to compare the expression of RTF during HIV infections with that during HCV infections. Three-color flow-cytometric analysis of peripheral blood collected from HIV(+) HCV-seropositive (HCV(+)), HIV- and HCV-seropositive (HIV(+) HCV(+)), and HIV- and HCV-seronegative (HIV(-) HCV(-)) individuals was performed. Levels of RTF expression on T-lymphocyte subsets from these groups were compared, as were levels of RTF expression on activated T cells expressing CD38 and HLA-DR, to determine the relationship of RTF expression to these infections. We demonstrated that the expression of RTF on surfaces of T cells from HIV(+) individuals is upregulated and that its expression on T cells from HCV(+) individuals is downregulated. A twofold increase in the mean channel fluorescence of RTF on CD3(+) T cells was seen in both HIV(+) and HIV(+) HCV(+) individuals compared to HIV(-) HCV(-) individuals. HCV(+) individuals had lower levels of RTF expression than HIV(-) HCV(-) individuals (P < 0.005 for CD4(+); P < 0.0005 for CD8(+)). In terms of percentages of T cells expressing RTF, the groups were ranked as follows: HIV(+) > HIV(+) HCV(+) > HIV(-) HCV(-) > HCV(+). The results indicate that RTF expression correlates with HIV-associated immune activation and may be associated with Th2-type responses.

Regeneration and tolerance factor: a correlate of human immunodeficiency virus-associated T-cell activation

Human immunodeficiency virus (HIV) infection causes extensive phenotypic alterations in lymphocytes. Cellular markers that are normally absent or expressed at low levels on quiescent cells are upregulated throughout the disease course. The transmembrane form of regeneration and tolerance factor (RTF) is expressed at negligible levels on resting T cells but is quickly upregulated following in vitro stimulation and activation. Recently, we reported that expression of RTF was significantly higher in cells from HIV-seropositive (HIV(+)) individuals than in cells from HIV-seronegative (HIV(-)) individuals. Because T cells from HIV(+) individuals express markers reflecting chronic activation, we hypothesized that these in vivo-activated cells would coexpress RTF. Flow cytometry was used to assess RTF expression on activated (CD38(+) and HLA-DR(+)) CD4(+) and CD8(+) T cells. HIV(+) individuals had higher percentages of RTF(+) CD38(+) (P < 0.0001) or RTF(+) HLA-DR(+) (P = 0.0001) CD4(+) T cells than HIV(-) individuals. In HIV(+) individuals, increased percentages of CD4(+) T cells that were RTF(+), RTF(+) CD38(+), and RTF(+) HLA-DR(+) correlated inversely with the absolute number and percentage of CD4(+) T cells and correlated positively with plasma beta(2)-microglobulin concentrations. HIV(+) individuals had higher percentages of CD8(+) T cells that were RTF(+) CD38(+) (P = 0.0001) or RTF(+) HLA-DR(+) (P = 0.0010). In HIV(+) individuals, increased percentages of CD8(+) T cells that were RTF(+) HLA-DR(+) correlated inversely with the percentage of CD4(+) T cells, and high percentages of CD8(+) T cells that were RTF(+) CD38(+) correlated positively with plasma beta(2)-microglobulin levels. These findings strongly suggest that increased RTF expression is a correlate of HIV-associated immune system activation.

Expression of regeneration and tolerance factor on B cell chronic lymphocytic leukemias: a possible mechanism for escaping immune surveillance

Regeneration and tolerance factor (RTF) is a protein expressed on developing tissue such as the thymus and the placenta. RTF has been reported to down-regulate cell-mediated immune responses. To examine the potential role of tumor-derived RTF to suppressing antitumor responses, we analyzed a panel of seven B cell tumor lines for the membrane RTF using a fluorescein isothiocyanate (FITC) conjugated monoclonal antibody, which reacts with membrane RTF. All the B cell tumor lines we examined express RTF on the cell surface. We also tested conditioned media from these B cell lines for their ability to suppress IL-2R expression on activated cells. Conditioned media from each B cell line suppressed IL-2R expression on activated Jurkat T cells and activated peripheral blood mononuclear cells. A monoclonal antibody to the biologically active portion of RTF reversed this suppressive activity. Finally, the tumor cell population from patients with chronic lymphocytic leukemia was found to express cell surface RTF. Thus, RTF expression could be a new mechanism used by tumor cells to escape immune surveillance.

Increased expression of regeneration and tolerance factor in individuals with human immunodeficiency virus infection

Regeneration and tolerance factor (RTF) plays a pivotal role in successful pregnancy outcome and has potent immunomodulating properties. During pregnancy, it is abundantly expressed in the placenta and on peripheral B lymphocytes. Several lines of evidence suggest that both successful pregnancy outcome and progression from human immunodeficiency virus (HIV) infection to AIDS are associated with a Th2-type response. As a result, we hypothesized that the cellular expression of RTF may also be increased during infection with HIV. Using flow cytometric analysis, we showed a significantly (P < 0.01) increased expression of RTF on CD3(+) cells obtained from individuals with HIV over that for individuals without HIV. On average, 32.1% of the CD3(+) cells from individuals with HIV expressed high levels of RTF. In contrast, an average of only 6.7% of the CD3(+) cells from individuals without HIV expressed high levels of RTF. Similar results were obtained when CD19(+) cells from individuals with (mean, 44.1%) and without (mean, 25.8%) HIV were evaluated. Linear regression analysis suggested that high levels of RTF expression by CD3(+) cells correlated better with viral load (r value, 0.46) than with absolute CD4 count (r value, 0.09). While additional experiments are necessary to delineate the precise immunologic role of RTF, our current data suggest that RTF expression during HIV infection may be a useful marker of immune activation.

Early pregnancy factor: an extracellular chaperonin 10 homologue

Early pregnancy factor (EPF) has been identified as a homologue of chaperonin 10 (cpn10) with immunosuppressive and growth factor properties. As a homologue of cpn10, it belongs to the heat shock family of proteins (hsp) but, unlike other members of this family, EPF is detected extracellularly. Early pregnancy factor was first discovered in pregnancy serum by the rosette inhibition test, and the novelty of its discovery was that its presence could diagnose pregnancy within 6-24 h of a fertile mating. As well as being a monitor of the presence of a viable embryo, it is necessary for embryonic survival. In this capacity it acts as both an immunosuppressant and growth factor. Early pregnancy factor is also a product of proliferating primary and neoplastic cells and functions as an autocrine growth factor both in vivo and in vitro. It has a modifying effect on the outcome of experimental autoimmune encephalomyelitis, an animal model of multiple sclerosis. Early pregnancy factor is considered to be one of the major factors involved in the modification of multiple sclerosis observed during pregnancy.

TJ6: the pregnancy-associated cytokine

These studies have demonstrated that TJ6m protein can be measured in women prior to a spontaneous abortion based on expression of TJ6 on CD56-positive NK cells. This suggested to us a possible regulator function for TJ6 during pregnancy. We have shown that in T cells only crosslinking of the T-cell receptor can upregulate TJ6 expression and the other activators, such as mitogens, do not. A clear discrepancy in the pattern of expression of TJ6 on CD56 and CD19-positive cells was noted between successful and unsuccessful pregnancies. A successful pregnancy is denoted by TJ6 expression on B cells, whereas in a potential spontaneous abortion there is TJ6 expression on both NK and B cells.

Transforming growth factor-beta 2-related-decidual suppressor factor is not related to TJ6 protein

Transforming growth factor (TGF)-beta 2-related-decidual suppressor factor (DSF) and TJ6 protein are both immunosuppressive molecules present in murine and human pregnancy. Treatment of mice with either anti-TJ6 or anti-TGF-beta 2 neutralizing antibodies results in increased fetal loss. Western blots of supernatants from pregnant mouse decidua probed with anti-TJ6 (soluble form) showed a doublet at a similar molecular size as when the blot was probed with anti-TGF-beta 2 antibody. The problem is to determine whether TJ6 and DSF are the same protein. In order to determine if TJ6 and DSF are the same or different proteins, we used affinity column purified TGF-beta 2-DSF and stained Western blots with anti-TJ6. The TGF-beta 2-monoclonal antibody affinity column-purified DSF that stained with anti TGF-beta 2 was not reactive with anti-TJ6 antibody. TJ6 has only a 30% gene sequence homology and a 13% amino acid homology to TGF-beta 2. TJ6 and TGF-beta 2-related DSF appear to be different immunosuppressive proteins in decidua.

Expression of membrane form of the pregnancy associated protein TJ6 on decidual lymphocytes in the first trimester of pregnancy

TJ6, a newly described protein produced locally in the uterine decidua during pregnancy, may be involved in maintaining a unique immunological environment at the maternal-fetal interface. The aim of this study was to determine whether TJ6 is expressed as membrane form on decidual lymphocytes (DL), to define the phenotypes of TJ6m (membrane form TJ6) expressing cells and to analyze the fluorescence intensity of TJ6m expression. Peripheral blood lymphocytes (PBL) and DL were obtained from first trimester pregnancies undergoing elective termination and immunophenotyped for TJ6m and other cell surface antigens (CD3, CD8, CD19, CD56, CD16) by flow cytometry. This is the first study showing that TJ6 molecules are present on decidual lymphocytes in human pregnancy. TJ6m expression on PBL was not different from that of DL. However, a significantly higher percentage of double positive (TJ6m+CD3+, TJ6m+,CD8+,TJ6m+CD19+) cells were found in PBL when compared to DL. The average fluorescence intensity (AFI) for the TJ6m marker among cells with CD8+, CD19+ and CD56+ double positive was significantly higher in DL as compared with those of PBL. The AFI for granularity of double positive DL was significantly higher than observed in PBL.

Reciprocal alteration in circulating TJ6+ CD19+ and TJ6+ CD56+ leukocytes in early pregnancy predicts success or miscarriage

PROBLEM

TJ6 is a cytokine whose membrane form is regularly expressed on the B lymphocytes of women during pregnancy. In a previous study we have shown that pregnancies that end in a spontaneous abortion are characterized by an increase in natural killer (NK) cells and that NK cells in these pregnancies also expressed TJ6, whereas NK cells from pregnancies that terminate normally neither increase in number nor do they express significant amounts of the cytokine.

METHODS

To evaluate the ability of TJ6 to predict pregnancy outcome, 61 blood samples from pregnant women were studied. Blood samples were drawn between 5 and 12 weeks of gestation and analyzed for lymphocyte expression of TJ6 using Cytoron Absolute flow cytometry and two-color fluorescence. The percentage of CD19+ (B) cells and CD56+ (NK) cells that expressed TJ6 was calculated, and this percentage was correlated with subsequent pregnancy outcome classified as successful (viable birth) or unsuccessful (abortion, stillbirth). TJ6 CD19 and TJ6 CD56 was determined in 32 blood samples from women with successful pregnancy outcomes and 29 samples from women with unsuccessful pregnancy outcome.

RESULTS

The mean TJ6 CD19 expression for successful pregnancies was 10.6% and for unsuccessful pregnancies was 5.1% (P < 0.03). The mean TJ6 CD56+ percentage of circulating cells that express TJ6 expression for successful pregnancies was 3.3% and for unsuccessful pregnancies was 10.4% (P = 0.02). All unsuccessful pregnancies had less than 90% of circulating CD19 cells express TJ6 and/or greater than 50% of circulating CD56 cells express TJ6. Use of the expression of TJ6 on CD19 and CD56 cells during the first trimester predicts viable pregnancy with a sensitivity of 100%, specificity of 100%, positive predictive value of 100%, and negative predictive value of 100%.

CONCLUSIONS

The work now being reported validates the hypothesis that expression of TJ6 on NK cells obtained from pregnant women predicts the outcome of pregnancy. In addition we show that this prognosticator can be reliably demonstrated early in the first trimester.