Inhibition of vacuolar ATPase subunit in tumor cells delays tumor growth by decreasing the essential macrophage population in the tumor microenvironment.

In cancer cells, vacuolar ATPase (V-ATPase), a multi-subunit enzyme, is expressed on the plasma as well as vesicular membranes and critically influences metastatic behavior. The soluble, cleaved N-terminal domain of V-ATPase a2 isoform is associated with in vitro induction of tumorigenic characteristics in macrophages. This activity led us to further investigate its in vivo role in cancer progression by inhibition of a2 isoform (a2V) in tumor cells and the concomitant effect on tumor microenvironment in the mouse 4T-1 breast cancer model. Results showed that macrophages cocultivated with a2V knockdown (sh-a2) 4T-1 cells produce lower amounts of tumorigenic factors in vitro and have reduced ability to suppress T-cell activation and proliferation compared with control 4T-1 cells. Data analysis showed a delayed mammary tumor growth in Balb/c mice inoculated with sh-a2 4T-1 cells compared with control. The purified CD11b(+) macrophages from sh-a2 tumors showed a reduced expression of mannose receptor-1 (CD206), interleukin-10, transforming growth factor-ß, arginase-1, matrix metalloproteinase and vascular endothelial growth factor. Flow cytometric analysis of tumor-infiltrated macrophages showed a significantly low number of F4/80(+)CD11c(+)CD206(+) macrophages in sh-a2 tumors compared with control. In sh-a2 tumors, most of the macrophages were F4/80(+)CD11c(+) (antitumor M1 macrophages) suggesting it to be the reason behind delayed tumor growth. Additionally, tumor-infiltrating macrophages from sh-a2 tumors showed a reduced expression of CD206 compared with control whereas CD11c expression was unaffected. These findings demonstrate that in the absence of a2V in tumor cells, the resident macrophage population in the tumor microenvironment is altered which affects in vivo tumor growth. We suggest that by involving the host immune system, tumor growth can be controlled through targeting of a2V on tumor cells.

Tumor-associated vacuolar ATPase subunit promotes tumorigenic characteristics in macrophages.

Macrophage polarization contributes to distinct human pathologies. In tumors, a polarized M2 phenotype called tumor-associated macrophages (TAMs) are associated with promotion of invasion and angiogenesis. In cancer cells, vacuolar ATPase (V-ATPase), a multi-subunit enzyme, is expressed on the plasma/vesicular membranes and critically influences the metastatic behavior. In addition, the soluble, cleaved N-terminal domain of a2 isoform of V-ATPase (a2NTD) is associated with in vitro induction of pro-tumorigenic properties in monocytes. This activity of a2 isoform of V-ATPase (a2V) caused us to investigate its role in cancer progression through the evaluation of the immunomodulatory properties of a2NTD. Here, we present direct evidence that surface expression of V-ATPase is associated with macrophage polarization in tumor tissue. Macrophages from BALB/c mice (peritoneal/bone marrow derived) were stimulated with recombinant a2NTD in both ex vivo and in vivo systems and evaluated for TAM characteristics. a2V was highly expressed in tumor tissues (breast and skin) as well as on the surface of tumor cell lines. The a2NTD-stimulated macrophages (a2MΦ) acquired TAM phenotype, which was characterized by elevated expression of mannose receptor-1, Arginase-1, interleukin-10 and transforming growth factor-ß. a2MΦ also exhibited increased production of other tumorigenic factors including matrix metalloproteinase-9 and vascular endothelial growth factor. Further, a2MΦ were cocultured with mouse B-16F0 melanoma cells for their functional characterization. The coculture of these a2MΦ subsequently increased the invasion and angiogenesis of less invasive B-16F0 cells. When cocultured with naive T cells, a2MΦ significantly inhibited T-cell activation. The present data establish the role of V-ATPase in modulating a macrophage phenotype towards TAMs through the action of a2NTD, suggesting it to be a potential therapeutic target in cancer.

Increased T helper 1 cytokine responses by circulating T cells are present in women with recurrent pregnancy losses and in infertile women with multiple implantation failures after IVF.

BACKGROUND: We aimed to study T-helper 1 (Th1) and Th2 intracellular cytokine expression in peripheral blood lymphocytes of women with recurrent spontaneous abortions (RSA) or infertility with multiple implantation failures after IVF cycles. METHODS: Twenty-six women with three or more RSA and 23 with two or more IVF failures (14 with no history of spontaneous abortion (SAB) and nine with more than one SAB) comprised the two study groups. Twenty-one non-pregnant healthy multiparous women served as controls. Proportions (%) of lymphocytes containing IFN-gamma, TNF-alpha, IL-4 and IL-10 and the Th1/Th2 ratios of IFN-gamma/IL-4, IFN-gamma/IL-10, TNF-alpha/IL-4 and TNF-alpha/IL-10 in CD3+, CD3+/CD8- (T helper) and CD3+/CD8+ (T suppressor) cells were measured by 4-colour flow cytometry. RESULTS: RSA women demonstrated significantly higher Th1/Th2 ratios of IFN-gamma/IL-4 (P < 0.01), TNF-alpha/IL-4 and TNF-alpha/IL-10 (P < 0.05 each) in CD3+/CD8- T helper cells than those of controls. The proportion of TNF-alpha producing CD3+/CD8- cells (P < 0.05), and the Th1/Th2 ratios of TNF-alpha/IL-4 (P < 0.05) and TNF-alpha/IL-10 (P < 0.005) in CD3+/CD8- cells were significantly higher in women with multiple IVF failures without SAB as compared with those of controls. CONCLUSIONS: The prevalence of dominant Th1 immune responses in peripheral blood lymphocytes may reflect the systemic contribution of Th1 cytokines to RSA or multiple implantation failures in IVF cycles.

Expression of a novel protein by regenerating hepatocytes and peripheral blood lymphocytes.

Regeneration and tolerance factor (RTF) is a protein with immunosuppressive activity and is normally present in the thymus and placenta. RTF was measured in the livers of patients with regenerating nodules due to alcoholic cirrhosis and hepatitis C. RTF was expressed in the regenerating nodules of 26 patients with alcoholic cirrhosis. All patients with chronic hepatitis C without cirrhosis failed to express RTF. Flow cytometry revealed upregulation of RTF on the lymphocytes from alcoholic cirrhosis and downregulation in hepatitis C disease.

Regeneration and tolerance factor is expressed during T-lymphocyte activation and plays a role in apoptosis.

Regeneration and tolerance factor (RTF) is a protein cloned from the thymus and expressed on B lymphocytes in normal pregnancy, B lymphocytic leukemia lines, and T and B lymphocytes in individuals with HIV infection. Findings, using the Jurkat T-cell model, revealed that RTF is upregulated after activation and anti-RTF antibody-induced apoptosis. In this article anti-RTF antibody-induced apoptosis of both unstimulated and activated T lymphocytes. RTF expression was examined in human PBMC or purified T lymphocytes after their in vitro activation. Kinetic studies indicated maximal RTF cell surface expression on activated T lymphocytes occurred between expression of the early activation antigen CD69 and the IL-2alpha receptor (CD25) by multiparameter flow cytometry. RTF receptor expression correlated with Fas (CD95) and CD25 receptor expression (r2 = 0.6 and 0.5, respectively). RTF surface expression was dependent on the stimuli used to activate T lymphocytes. T lymphocytes obtained maximal RTF expression when activated through the TCR signal complex using anti-CD3epsilon antibody alone when compared with T lymphocytes activated with costimulation provided by anti-CD28 antibody alone or with anti-CD28 and anti-CD3epsilon antibody. RTF is expressed under conditions of both activation and anergy. The RTFs increased concentration on the surface of anergic T cells may protect these cells from apoptosis because increased RTF concentrations inhibited anti-RTF induced apoptosis. These data further characterize the expression of RTF on activated T lymphocytes and the role of anti-RTF antibody in T-lymphocyte apoptosis.

Status of peripheral blood natural killer cells in women with recurrent spontaneous abortions and infertility of unknown aetiology.

The aim of this study was to investigate the functional status and immunophenotypic characteristics of natural killer (NK) cells in women who suffer recurrent spontaneous abortions (RSA) or have infertility of unknown aetiology. Peripheral blood mononuclear cells (PBMC) were obtained from 40 study patients and 13 normal healthy multiparous controls. NK cells were identified using anti-CD56 and anti-CD16 monoclonal antibodies (mAb). The expression of CD69, CD25, CD122, CD30, CD154, CD128 and CD94 on NK cells was detected using specific mAb and analysed by flow cytometry. CD69 expression on NK cells after ED(27) human trophoblast cell line co-culture with PBMC was also investigated. A significant increase in CD69 expression on CD56(+) NK cells was demonstrated in women with RSA (P < 0.005) and infertility (P < 0.05) as compared with that of normal controls. Conversely, CD94 expression was significantly decreased in women with RSA (P < 0.005) and infertility (P < 0.05) in comparison with that of controls. Increased CD69 expression on NK cells was induced after 24 h co-culture with ED(27). In conclusion, peripheral blood NK cells of women with RSA and infertility of unknown aetiology have higher proportions of activated NK cells in vivo. Unbalanced CD69 and CD94 expression may explain the underlying pathology.

Regeneration and tolerance factor of the human placenta induces IL-10 production.

Regeneration and tolerance factor (RTF) was originally identified in the placenta of mice and the isolated protein shown to have suppressive effects. In these studies, the gene cloned from thymus tissue was mapped to human chromosome 12. The role of recombinant RTF on cytokines was examined. In addition, we examined the human placenta by immunohistochemistry for RTF expression. RTF was expressed at the peripheral layer of cytotrophoblast in 7-9-week-old placentas. Using the RTF gene sequence, a recombinant protein was prepared and shown to induce IL-10 production. These data indicate that RTF is expressed by the tissues most intimately involved at the maternal-fetal interface, and its biological activity is capable of producing the necessary immune response for initiating and maintaining the maternal-fetal relationship.

Regeneration and tolerance factor's potential role in T-cell activation and apoptosis.

Regeneration and tolerance factor (RTF) is a novel membrane protein that has a diverse expression pattern and immunoregulatory properties. RTF is expressed in vivo on the surface of individuals with B cell chronic lymphocytic leukemia and on activated T lymphocytes of HIV infected individuals as determined by their coexpression with CD38 and HLA-DR. The unique expression patterns of this protein in vivo lead us to investigate its expression in vitro. The activation of human PBMCs through the TCR, using anti-CD3 antibody and PMA, upregulated cell surface expression of RTF from 2. 3% to 91.2% (mean channel fluorescence [MCF] increased threefold). The activation of Jurkat T cells through the TCR upregulated surface expression of RTF from 8.3% (MCF-1.3) to 58.7% (MCF-13.1). The Jurkat T-cell line was used as a model system to explore RTF's role in cellular activation. Using the Jurkat T-cell model, we found anti-RTF antibody induces apoptosis. The addition of anti-RTF antibody increased annexin V binding by threefold compared with the IgG1 kappa isotype control antibody (p < 0.00002) and activated caspase 3. These data indicate that RTF is expressed during T-cell activation and may be associated with apoptosis.

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.

Clarithromycin-induced alterations in vaginal flora.

Many antibiotics have been shown to alter both the bacterial and the fungal flora of the vagina, in some cases potentially increasing a woman's propensity toward urinary tract infections and vaginal candidiasis. The effects of some of the newer macrolide antibiotics on women's vaginal flora have not been previously studied, and almost none of the previous studies specifically cultured for effects on vaginal lactobacillus. Young women (ages 18-45 years) who were about to go onto therapy with clarithromycin, who did not have any conditions known to affect the vaginal flora (eg, diabetes mellitus, spermicide use, menopausal status without hormone replacement therapy), and who agreed to participate in the study were cultured with aerobic and anaerobic and fungal vaginal cultures before starting the antibiotic. These same women were then retested about 4 to 6 weeks after the start of their antibiotic course, and the results of their preantibiotic and postantibiotic cultures were compared. Lactobacillus was present in 33% of patients by vaginal culture before treatment, but this decreased to 0% after treatment. Escherichia coli was present in only 8% of patients before treatment, but this increased to 17% of patients after treatment. Enterococcus was present in 25% of patients before treatment but in only 8% of patients after treatment. The incidence of Gardnerella vaginalis was not affected by the treatment. Candida species incidence increased from 17% to 33% with treatment. The overall effects of clarithromycin on the vaginal flora are similar to other older antibiotics that have been tested.

Immunoglobulin G infusion treatment for women with recurrent spontaneous abortions and elevated CD56+ natural killer cells.

We aimed to investigate the clinical effect of intravenous immunoglobulin G (IVIg) treatment in recurrent aborters with elevated peripheral blood CD56+ NK cell levels while on lymphocyte immunization, anticoagulation and prednisone treatment, with respect to subsequent live birth and reproductive outcome. Thirty-three women with recurrent abortions achieved alloimmune recognition after lymphocyte immunizations. All had autoimmune abnormalities and received preconception anticoagulation and prednisone treatment. At the time of positive pregnancy testing, 18 women with normal NK cell levels (<12%) and 6 with elevated NK cell levels (>12%) continued anticoagulation and prednisone treatment, and 9 with elevated NK cell level initiated additional IVIg treatment. The live birth rates of women with elevated NK cell level (>12%) who initiated post-conception IVIg treatment in addition to anticoagulation and prednisone (100.0%), women with normal NK cell levels (<12%) who continued anticoagulation and prednisone (83.3%) and women with elevated NK cell level (>12%) who continued anticoagulation and prednisone (33.3%) are significantly different (P=0.0065). Prevalence of intrauterine growth retardation and preterm delivery among 3 study groups were not different. In conclusion, post-conception IVIg treatment significantly improves reproductive outcome in women with elevated CD56+ NK cells with pregnancy who received preconception lymphocyte immunization, anticoagulation and prednisone treatment.

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.

Natural killer (NK) cell subsets and NK cell cytotoxicity in women with histories of recurrent spontaneous abortions.

PROBLEM: Natural Killer (NK) cell measurement and NK cytotoxicity are two measurements for assessing the cellular immune response. Both of the techniques have been reported to be prognostic for women with recurrent spontaneous abortion (RSA). We evaluated the two methods to determine the relationship of the two assays. Because both methods portend to evaluate the same process, the previous clinical data suggested that the methods evaluate the same phenomena. We undertook these studies to determine whether simple NK cell counts may be sufficient in the evaluation of NK activity in RSA. METHOD OF STUDY: The NK cell cytotoxicity at effector-to-target ratios of 50:1 and 25:1 was determined using a flow cytometric NK cell cytotoxicity assay. These values were then correlated with the percentages and absolute counts of three peripheral blood NK cell subsets. RESULTS: The data indicate that the flow cytometric assay is reproducible and precise and can be successfully used to evaluate patient samples. Linear regression analysis indicated a lack of correlation between peripheral blood NK cell cytotoxicity and percentages or absolute counts of CD56+CD16+, CD56+CD16- or CD3+CD56+ lymphocyte subsets (range of correlation coefficients, 0.1-0.3). CONCLUSIONS: NK cell cytotoxicity and peripheral blood NK cell values measure different aspects of NK cells and do not correlate. These data indicate that simple enumeration of NK cells may not be sufficient in the evaluation of NK cells in RSA.

Natural killer cell cytotoxicity and paternal lymphocyte immunization in women with recurrent spontaneous abortions.

PROBLEM: Natural killer (NK)-cell cytotoxicity in women undergoing lymphocyte immunization prior to and following treatment was investigated. METHOD OF STUDY: A cohort of 33 women with a history of two or more recurrent spontaneous abortions was prospectively studied. NK-cell cytotoxicity was determined at effector-to-target ratios of 50:1 and 25:1. Peripheral blood CD56+ NK-cell, CD19+ B-cell, CD19+/5+ B-1-cell, and CD3+ pan T-cell levels were studied by flow cytometry before and after lymphocyte immunization treatment. Maternal antipaternal T- and B-cell antibody levels were measured before and after lymphocyte immunization by flow cytometric analysis. Paternal lymphocyte immunizations were given two times with a 4-week interval. Post-lymphocyte immunization testing was done 4 weeks after the second lymphocyte immunization. The controls were 8 normal healthy women. NK assays were done twice with an interval of 8 weeks. RESULTS: NK-cell activity at effector-to-target ratios of 50:1 (P = 0.005) and 25:1 (P = 0.001) were significantly suppressed after lymphocyte immunization. CD3+ pan T-cell levels after lymphocyte immunization were significantly increased compared with levels before lymphocyte immunization (P = 0.008). CD56+ NK-cell levels were significantly suppressed after lymphocyte immunization (P = 0.016). There was no correlation between changes in NK cytotoxicity and differences in antipaternal lymphocyte antibody levels before or after lymphocyte immunization. CONCLUSION: Lymphocyte immunization suppresses NK-cell cytotoxicity and CD56+ NK-cell levels and increases the peripheral blood CD3+ T-cell population in women with recurrent spontaneous abortions.

Expression of TJ6 during pregnancy.

PROBLEM: TJ6 will be one of the molecules involved in fetal-specific immune suppression during pregnancy. In the mouse and human decidua, the regulation of uterine natural killer (uNK) cells is important during pregnancy. METHOD OF STUDY: To further understand the possible functions of TJ6 during pregnancy, syngeneic, allogeneic, and mutant mice were examined for TJ6 expression. RESULTS: Immunoblotting showed that TJ6 protein was expressed on most of the placenta-associated mononuclear cells, and the size was 70-72 kDa at all stages of pregnancy. The expression of TJ6 mRNA was studied by a ribonuclease protection assay in syngeneic and allogeneic matings, and in immune-deficient mice of genotypes scid/scid and scid/scid.bg/bg. CONCLUSIONS: Genetic disparity, lack of T and B lymphocytes, and loss of NK lytic function had no significant effect on the expression of TJ6 mRNA.

Effect of intravenous immunoglobulin G on natural killer cell cytotoxicity in vitro in women with recurrent spontaneous abortion.

Intravenous immunoglobulin (IVIg) has been used to treat women with recurrent spontaneous abortion (RSA), particularly for women with elevated natural killer (NK) cells. We investigated the effect of IVIg on peripheral blood NK cell activity in vitro in women with RSA. 51Cr-release assays using K562 in the presence of varying concentrations of IVIg were performed using PBL from 16 women with RSA. Antibody dependent cellular cytotoxicity (ADCC) was evaluated using Daudi cells. Effectors and targets were preincubated with IVIg. Binding of IVIg to K562 and Daudi was evaluated by flow cytometry. The effect of K562 absorbed IVIg on NK activity was compared to that of non-absorbed IVIg. NK cytotoxicity and ADCC in the presence of F(ab')2 fragments were compared with those in the presence of intact IVIg. IVIg produced a significant, dose dependent inhibition of NK activity in vitro. Inhibition of NK activity occurred when effectors but not targets were preincubated with IVIg. IVIg binds to K562 and Daudi. IVIg increased ADCC when targets but not effectors were incubated with IVIg. K562 absorbed IVIg produced more inhibition of NK cytotoxicity than non-absorbed IVIg. Suppression of NK cytotoxicity by F(ab')2 was as effective as that of IVIg. However, F(ab')2 did not increase ADCC. IVIg effectively reduces peripheral blood NK cytotoxicity in vitro. Inhibition of NK cytotoxicity is mediated at the effector cell level through the antigen binding portion of the immunoglobulins. Women with RSA and elevated NK cells may benefit from IVIg treatment.

Intravenous immunoglobulin inhibits natural killer cell activity in vivo in women with recurrent spontaneous abortion.

We previously reported elevation of natural killer (NK) cells in women with recurrent spontaneous abortion (RSA) of immune etiology. In this study, we investigated the effect of intravenous immunoglobulin G (IVIg) on peripheral blood NK activity in vivo in women with RSA. Blood was drawn prior to and 7-11 days after IVIg therapy in eight women with RSA. NK activity was measured using K562 as target cells for 51Cr-release assays. Serum IgG concentrations were also measured. All received 400 mg/kg/day of IVIg for 3 consecutive days. 1) Seven of eight women became pregnant. Five delivered a live born infant. Three out of five women (60%) who delivered a live born infant showed a significant inhibition of NK cytotoxicity post IVIg and the rest did not show any changes; 2) NK cytotoxicity was significantly increased in a woman who miscarried again; 3) A woman who miscarried a chromosomally abnormal fetus showed a significant inhibition of NK cytotoxicity after IVIg; and 4) Serum IgG concentration increased significantly from 9.3 +/- 3.0 mg/ml to 23.5 +/- 5.1 mg/ml post IVIg therapy. IVIg effectively inhibits peripheral blood NK activity in vivo. These results are consistent with our previous finding showing that IVIg inhibits NK cell activity in vitro. Women with RSA and elevated NK cells may benefit from IVIg treatment.