Expression of CD16, CD18 and CD56 in tributyltin-exposed human natural killer cells

Tributyltin (TBT) was produced in large quantities for use in wood preservation, marine antifouling paints, disinfection of circulating industrial cooling waters and slime control in paper mills. TBT is found in dairy products, meat and fish. We and others have shown that there are measurable levels of TBT in human blood. BTs appear to increase the risk of cancer and viral infections in exposed individuals. In previous studies, we demonstrated that the NK-cytotoxic function of lymphocytes was greatly diminished after a 1-h exposure to 300 nM TBT or a 24-h exposure to 200 nM TBT. Inhibition induced by a 1-h exposure to 300 nM TBT continues even after removal of the compound. There is also decreased ability of NK cells to bind to tumor target cells when they have been exposed to 200 nM TBT for 24 h. This loss of binding function is not seen when NK cells are exposed to 300 nM TBT for 1 h. However, NK cells exposed to 300 nM TBT for 1 h and then incubated in TBT-free media for 24, 48 or 96 h, show a significant loss of tumor-binding function by 96 h. The effects of TBT on cell surface molecules that are crucial to NK cell function is investigated. The data indicate there is a loss of expression of CD16 and CD56 on NK cells exposed to 200 nM TBT for 24 h. There is no decrease in expression of any of the markers studied when NK cells are exposed to 300 nM TBT for 1 h, consistent with the fact that a 1-h exposure has no effect on the ability of NK cells to bind to tumor targets. However, when NK cells are exposed to 300 nM TBT followed by 24, 48 or 96 h incubations in TBT-free media, there is a significant loss of CD16 and CD18 expression after 24 h and of CD16 and CD56 expression after 48 and 96 h.

Senescence in innate immune responses: reduced neutrophil phagocytic capacity and CD16 expression in elderly humans

Elderly humans are more susceptible to bacterial infections because of declining immune status. We have investigated the effect of aging on neutrophil bactericidal responses, comparing neutrophil function in healthy, young (23-35 years) and elderly (>65 years) volunteers. Superoxide generation in response to fMLP was slightly increased in neutrophils from elderly donors, and serum from the elderly was able to opsonize E. coli efficiently. In contrast, phagocytic index was significantly lower in neutrophils from the elderly, compared with young donors (P<0.005). CD11a and CD11b expression was not affected by age, but CD16 was significantly reduced in neutrophils from elderly donors (P<0.0001). CD16 expression and phagocytic index were measured in the same neutrophils using FITC-labeled E. coli, PE-conjugated anti-CD16 antibody, and CD16 expression correlated with phagocytic index (r=0.83; P<0.05). In elderly patients with bacterial infection, CD16 expression remained low. We propose that reduced neutrophil CD16 expression and phagocytosis contribute to human immunesenescence.

Receptor modulation by Fc gamma RI-specific fusion proteins is dependent on receptor number and modified by IgG

The high-affinity IgG receptor, FcgammaRI (CD64), is constitutively expressed exclusively on professional APCs. Human FcgammaRI binds monomeric IgG with high affinity and is, therefore, saturated in vivo. The binding of IgG to FcgammaRI causes receptor recycling, while Abs that cross-link FcgammaRI cause rapid down-modulation of surface FcgammaRI. Because studies performed in the absence of ligand may not be representative of FcgammaRI modulation in vivo, we investigated the ability of FcgammaRI-cross-linking Abs and non-cross-linking derivatives to modulate FcgammaRI in the presence and absence of ligand. In the absence of ligand mAb H22 and wH22xeGFP, an enhanced green fluorescent protein (eGFP)-labeled fusion protein of H22, cross-linked and rapidly down-modulated surface FcgammaRI on the human myeloid cell line, U937, and its high FcgammaRI-expressing subclone, 10.6. This effect was dependent on the concentration of fusion protein and the level of FcgammaRI expression and correlated with internalization of both wH22xeGFP and FcgammaRI, itself, as assessed by confocal microscopy. A single-chain Fv version, sFv22xeGFP, which does not cross-link FcgammaRI, was unable to modulate FcgammaRI in the absence of IgG. However, if ligand was present, treatment with either monovalent or cross-linking fusion protein led to intracellular receptor accumulation. These findings suggest at least two alternate mechanisms of internalization that are influenced by ligand and demonstrate the physiologic potential of FcgammaRI to transport a large antigenic load into APCs for processing. These studies may lead to the development of better FcgammaRI-targeted vaccines, as well as therapies to down-modulate FcR involved in autoimmune diseases.

CD16+ and CD16- human blood monocyte subsets differentiate in vitro to dendritic cells with different abilities to stimulate CD4+ T cells

Experimental protocols for cancer immunotherapy include the utilization of autologous monocyte-derived dendritic cells (moDC) pulsed with tumor antigens. However, disease can alter the characteristics of monocyte precursors and some patients have increased numbers (up to 40%) of the minor CD16(+) monocyte subpopulation, which in healthy individuals represent 10% of blood monocytes. At the present, the capacity of CD16(+) monocytes to differentiate into DC has not been evaluated. Here, we investigated the ability of CD16(+) monocytes cultured with granulocyte- macrophage colony-stimulating factor, IL-4 and tumor necrosis factor-alpha to generate DC in vitro, and we compared them to DC derived from regular CD16(-) monocytes. Both monocyte subsets gave rise to cells with DC characteristics. They internalized soluble and particulate antigens similarly, and both were able to stimulate T cell proliferation in autologous and allogeneic cultures. Nevertheless, CD16(+) moDC expressed higher levels of CD86, CD11a and CD11c, and showed lower expression of CD1a and CD32 compared to CD16(-) moDC. Lipopolysaccharide-stimulated CD16(-) moDC expressed increased levels of IL-12 p40 mRNA and secreted greater amounts of IL-12 p70 than CD16(+) moDC, whereas levels of transforming growth factor-beta1 mRNA were higher on CD16(+) moDC. Moreover, CD4(+) T cells stimulated with CD16(+) moDC secreted increased amounts of IL-4 compared to those stimulated by CD16(-) moDC. These data demonstrate that both moDC are not equivalent, suggesting either that they reach different stages of maturation during the culture or that the starting monocytes belong to cell lineages with distinct differentiation capabilities.

Unique subpopulations of CD56+ NK and NK-T peripheral blood lymphocytes identified by chemokine receptor expression repertoire

CD56, an adhesion molecule closely related to neural cell adhesion molecule, is an immunophenotypic marker for several unique populations of PBLS: Although CD56(+) cells derive from multiple lymphocyte lineages, they share a role in immunosurveillance and antitumor responses. We have studied the chemokine receptor expression patterns and functional migratory responses of three distinct CD56(+) populations from human peripheral blood. NK-T cells were found to differ greatly from NK cells, and CD16(+) NK cells from CD16(-) NK cells. CD16(+) NK cells were the predominant population responding to IL-8 and fractalkine, whereas NK-T cells were the predominant population responding to the CCR5 ligand macrophage-inflammatory protein-1beta. CD16(-) NK cells were the only CD56(+) population that uniformly expressed trafficking molecules necessary for homing into secondary lymphoid organs through high endothelial venule. These findings describe a diverse population of cells that may have trafficking patterns entirely different from each other, and from other lymphocyte types.

Increased distribution and expression of CD64 on blood polymorphonuclear cells from patients with the systemic inflammatory response syndrome (SIRS)

Evidence is growing to suggest that the multiple organ damage of the systemic inflammatory response syndrome (SIRS) arises from the untoward activity of blood polymorphonuclear cells (PMNs), which upon activation acquire the IgG high affinity receptor, CD64. In the current study, flow cytometry was used to assess the prevalence of CD64-bearing PMNs and the intensity of expression of CD64 in whole blood samples from 32 SIRS patients, 11 healthy normal subjects and from eight non-SIRS patients in the intensive care unit (ICU). The percentage of PMNs expressing CD64 was higher in SIRS patients (mean 65%) than in non-SIRS patients (mean 42%; P < 0.02) and in healthy controls (mean 19%; P < 0.001) and was particularly evident in patients with SIRS and sepsis (mean 71%; P < 0.02) as opposed to SIRS alone (mean 55%). There were more CD64 molecules expressed on PMNs from patients with SIRS (median 1331 molecules/cell) in comparison with PMNs from healthy subjects (median 678 molecules/cell; P < 0.01). The highest intensity of CD64 expression was associated with PMNs from patients with both SIRS and sepsis. Functional studies revealed that the supranormal binding of PMNs from patients with SIRS to endothelial monolayers treated with TNFalpha was impeded by anti-CD64 antibodies (mean 24% inhibition; P < 0.01). Monitoring the distribution of CD64+ PMNs and their level of CD64 expression could be of assistance in the rapid discrimination of patients with SIRS from other ICU patients and in the identification of PMNs which are likely to participate in the pathological manifestations of the disease.

Increased histidine decarboxylase expression during in vitro monocyte maturation; a possible role of endogenously synthesised histamine in monocyte/macrophage differentiation

OBJECTIVE

In this study the expression of histidine decarboxylase (HDC), the pivotal enzyme in histamine formation and the effect of endogenously produced histamine on differentiation antigens was examined during in vitro differentiation of human monocytes.

MATERIAL AND TREATMENT

Human elutriated monocytes from healthy volunteers were incubated with macrophage colony stimulating factor (M-CSF) and the expression of HDC was followed at both mRNA and protein levels. To study the possible function of histamine we followed the expression of some cell surface markers (CD14, CD16, CD91, CD49d and CD11c) relevant for phagocytic differentiation upon incubation in the presence of different histamine inhibitors, an HDC inhibitor: S(+)-alpha-fluoromethyl-histidine HCl, (alphaFMH), a compound that disturbs the interaction of histamine with intracellular cyp450 moieties: N,N-diethyl-2-[4-(phenylmethyl) phenoxy]-ethanamine HCI, (DPPE); and H1 and H2 receptor antagonists, Triprolidine and Cimetidine.

RESULTS

During in vitro culture of elutriated human monocytes, in the presence of M-CSF, the gene expression and biosynthesis of HDC was considerably increased. The various antihistamine agents decreased the expression of the cell surface markers examined in this study.

CONCLUSIONS

These data support the elevation of HDC expression during human monocytic differentiation and the possibility that monocyte-derived histamine is partially involved in regulation of M-CSF induced in vitro human monocyte/macrophage phagocytic differentiation.

Biphasic response of NK cells expressing both activating and inhibitory killer Ig-like receptors

NK cells can co-express inhibitory and activating killer Ig-like receptors (KIR) recognizing the same HLA class I ligand. We present evidence from experiments with NK cells expressing both activating (KIR2DS2) and inhibitory (KIR2DL2 and KIR2DL3) receptors that the activating KIR can function without apparent interference from the inhibitory KIR. These studies used CD158b mAb that is equally reactive with KIR2DS2, KIR2DL2 and KIR2DL3. First, we show using plastic-immobilized CD158b mAb that the activating KIR2DS2 is stimulated, resulting in NK cell division and degranulation. Second, we show using soluble CD158b mAb and FcRII (+) P815 cells that high concentrations of CD158b mAb trigger the inhibitory KIR, whereas low concentrations stimulate the activating KIR2DS2 resulting in NK cell division and cytolysis. These results demonstrate that the activating KIR2DS2 can function on cells co-expressing the inhibitory KIR2DL2 and/or KIR2DL3, indicating the potential for independent function of activating KIR with natural ligand.

A dominant role for Fc gamma receptors in antibody-dependent corneal inflammation

Although production of specific Ab is a critical element of host defense, the presence of Ab in tissues leads to formation of immune complexes, which can trigger a type III Arthus reaction. Our studies on a mouse model of river blindness showed that Ab production is essential for recruitment of neutrophils and eosinophils to the cornea and for development of corneal opacification. In the current study, we determined the relative contribution of complement and FcgammaR interactions in triggering immune complex-mediated corneal disease. FcgammaR(-/-) mice, C3(-/-) mice, and immunocompetent control (B6/129Sj) mice were immunized s.c. and injected intrastromally with Onchocerca volvulus Ags. Slit lamp examination showed that control mice, C3(-/-) mice, and control mice injected with cobra venom factor developed pronounced corneal opacification, whereas corneas of FcgammaR(-/-) mice remained completely clear. Furthermore, recruitment of neutrophils and eosinophils to the corneal stroma was significantly impaired in FcgammaR(-/-) mice, but not in C3(-/-) mice or cobra venom factor-treated mice. We therefore conclude that FcgammaR-mediated cell activation, rather than complement activation, is the dominant pathway of immune complex disease in the cornea. These findings demonstrate a novel role for FcgammaR interactions in mediating ocular inflammation.

Enhancement of splenic-macrophage Fcgamma receptor expression by treatment with estrogens

Splenic-macrophage Fcgamma receptors (FcgammaRs) participate in the pathophysiologies of immune-complex diseases and in host defense against infection. Modulation of macrophage FcgammaR expression is an immuno-therapeutic target. Glucocorticoids, sex steroids, and dopaminergic drugs modulate macrophage FcgammaR expression. Previous data indicate that estradiol increases macrophage FcgammaR expression. Nevertheless, the effects of clinically used estrogens upon macrophage FcgammaR expression are unknown. We assessed the effects of treatment with commonly used estrogens on the expression of macrophage FcgammaRs using a guinea pig experimental model. Six estrogens have been studied: ethynylestradiol (Et), mestranol (M), chlortianisene (Ct), promestriene, 17-epiestriol, and 17beta-estradiol. Following in vivo treatment of guinea pigs, we determined the clearance of immunoglobulin G (IgG)-sensitized erythrocytes in vivo, the binding of IgG-sensitized erythrocytes by isolated splenic macrophages, and splenic-macrophage FcgammaR cell surface expression. Estrogens enhance the clearance of IgG-sensitized erythrocytes by increasing splenic-macrophage FcgammaR expression. Et, M, and Ct were more effective than the other estrogens. Flow cytometry and fluorescence microscopy with monoclonal antibodies demonstrated that estrogens increase the cell surface expression of FcgammaR1 and -2 more than that of FcgammaR2. These data indicate that treatment with commonly used estrogens enhances the clearance of IgG-sensitized cells by improving splenic-macrophage FcgammaR expression.

The Fc receptor for IgG (Fc gamma RII; CD32) on human neonatal B lymphocytes

B cells express an Fc receptor for IgG (FcgammaRII; CD32) which is involved in feedback inhibition of antibody production. Engagement of FcgammaRII during ligation of the antigen receptor provides an inhibitory signal. FcgammaRII exists as several isoforms, with FcgammaRIIb (which carries an immunoreceptor tyrosine-based inhibition motif; ITIM) being predominant form on adult B cells. The inhibitory role of FcgammaRIIb may be unhelpful to the infant, since primary exposure to infectious agents is likely to be in the presence of maternal IgG. We hypothesized that neonatal B cells would be less susceptible to feedback inhibition by antibody, either through the expression of activation-competent FcgammaRII isoforms (FcgammaRIIa and FcgammaRIIc) or through reduced expression of the inhibitory FcgammaRIIb isoforms. Cord and adult B cells were examined for expression of FcgammaRII isoforms using monoclonal antibodies and RT-PCR. In vitro assays were performed to assess susceptibility of cord and adult cells to FcgammaRII-mediated suppression. Although there is no phenotypic difference in FcgammaRII expression (FcgammaRIIb predominating on both adult and cord B cells), FcgammaRIIb is expressed at lower levels on cord cells. This quantitative difference in FcgammaRIIb expression may explain the reduced susceptibility of cord B cells to antibody-mediated inhibition observed in these experiments.

Opsonin receptor expression on peritoneal exudative and circulatory neutrophils in murine acute pancreatitis

Acute severe (necrotizing) pancreatitis is often associated with pancreatic or peripancreatic infection. Decreased bacterial clearance due to impaired immune defense may cause local infection. We investigated expressions of surface opsonin receptors (CD11b, complement receptor 3; CD32/CD16, immunoglobulin G Fc receptor) on local and circulatory neutrophils, in murine acute pancreatitis. The mild and severe forms of acute pancreatitis were induced by seven and 13 subcutaneous injections of caerulein, respectively. Peritoneal exudative and circulatory neutrophils were counted and assayed for receptor expressions by flow cytometry, serially at 1-72 hours after pancreatitis induction. Histologically, mild and severe forms showed edematous and necrotizing pancreatitis, respectively. The peritoneal exudative neutrophil count was greater in mild than in severe pancreatitis. Expressions of CD11b and CD32/CD16 on local neutrophils were upregulated early in mild pancreatitis. This upregulation was attenuated in severe pancreatitis. The circulatory neutrophil count was elevated in severe pancreatitis but was unchanged in mild pancreatitis. Opsonin receptor expression on circulatory neutrophils showed a transient, modest upregulation in the early phase of mild pancreatitis. Receptor-positive circulatory neutrophils showed a marked elevation that persisted throughout the course of severe pancreatitis. In conclusion, severe (necrotizing) pancreatitis is associated with reduced opsonin receptor expression on local neutrophils and enhanced expression on circulatory neutrophils, as compared with mild (edematous) pancreatitis. These changes may contribute to local infectious complications and multiple organ failure, in severe pancreatitis.

Production of TNF-alpha by human V gamma 9V delta 2 T cells via engagement of Fc gamma RIIIA, the low affinity type 3 receptor for the Fc portion of IgG, expressed upon TCR activation by nonpeptidic antigen

Human lymphocytes expressing the gammadelta TCR represent a minor T cell subpopulation found in blood. The majority of these cells express Vgamma9Vdelta2 determinants and respond to nonpeptidic phosphoantigens. Several studies have shown that, in vivo, the percentage of Vgamma9Vdelta2 T cells dramatically increases during pathological infection, leading to the hypothesis that they play an important role in the defense against pathogens. However, the specific mechanisms involved in this response remain poorly understood. It has been established that Vgamma9Vdelta2 T cells display potent cytotoxic activity against virus-infected and tumor cells, thereby resembling NK cells. In this study, we show that, upon stimulation by nonpeptidic Ags, Vgamma9Vdelta2 T cells express FcgammaRIIIA (CD16), a receptor that is constitutively expressed on NK cells. CD16 appears to be an activation Ag for Vgamma9Vdelta2 T cells. Indeed, ligation of CD16 on Vgamma9Vdelta2 T cells leads to TNF-alpha production. This TNF-alpha production, which is dependent (like that induced via the TCR-CD3 complex) on the activation of the p38 and extracellular signal-regulated kinase-2 mitogen-activated protein kinases, can be modulated by CD94 NK receptors. Therefore, it appears that Vgamma9Vdelta2 T cells can be physiologically activated by two sequential steps via two different cell surface Ags: the TCR-CD3 complex and the FcgammaRIIIA receptor, which are specific cell surface Ags for T lymphocytes and NK cells, respectively. This strongly suggests that, in the general scheme of the immune response, Vgamma9Vdelta2 T cells represent an important subpopulation of cells that play a key role in the defense against invading pathogens.

Differences in the expression of CD64 and mCD14 on polymorphonuclear cells and on monocytes in patients with septic shock

The present study was performed to clarify the time course of the expression of CD64, the Fc gamma receptor type I (FcgammaR1), and membrane-bound CD14 (mCD14), one of the major receptors for endotoxin, on polymorphonuclear leukocytes (PMN) and monocytes in 22 postoperative/post-traumatic patients with septic shock. Therefore, the expression of CD64 and mCD14, and serum concentrations of granulocyte colony-stimulating factor (G-CSF) and interferon-gamma (IFN-gamma) were determined by flow cytometric analysis and enzyme-linked immunosorbent assay (ELISA), respectively, from the first day of septic shock onwards over a period of 14 days. When compared to the values of 12 healthy controls, CD64 expression was elevated significantly on PMN and monocytes of the patients, whereas the expression of mCD14 was decreased significantly at all days. The initially increased expression of CD64 on PMN and monocytes decreased within the first days of septic shock. The already initially decreased mCD14 expression decreased further on PMN, but not on monocytes. Serum concentrations of G-CSF and IFN-gamma during the study period were significantly higher than those of the control group. The differences in the kinetics of CD64 and mCD14 expression in patients with septic shock may be explained by different regulatory effects of cytokines, such as G-CSF and IFN-gamma.

CD14(dim)/CD16(bright) monocytes in hemophagocytic lymphohistiocytosis

Hemophagocytic lymphohistiocytosis (HLH) is an extremely rare and highly lethal chronic inflammatory disease, which is mediated by proinflammatory cytokines. In the peripheral blood of a boy suffering from HLH, a chronic expansion of CD14(dim)/CD16(bright) inflammatory monocytes was detected. Compared with CD14(bright) monocytes, their immunophenotype correlated with more mature monocytic cells differentiating to macrophages: they showed lower expression of CD11b, CD64 and CD35. Such CD14(dim)/CD16(bright) monocytes produce the inflammatory cytokines IL-1beta, IL-6 and TNF-alpha. They fit in well with the pathophysiological concept of HLH as an inflammatory state of lymphocytes and of the monocyte/macrophage system. In the presented patient the percentage of these circulating inflammatory monocytes decreased over time during clinical response to immunosuppressive therapy. This finding may indicate that CD14(dim)/CD16(bright) monocytes represented the degree of inflammation in this extremely rare and highly lethal disease.

Enhancement of polymorphonuclear cell-mediated tumor cell killing on simultaneous engagement of fcgammaRI (CD64) and fcalphaRI (CD89)

Antibodies can efficiently induce antitumor responses via recruitment of Fc receptor-bearing cytotoxic cells. Polymorphonuclear (PMN) cells represent attractive effector cells for antibody-directed immunotherapy. This, because activated PMN cells coexpress the class I receptors for IgG (FcgammaRI, CD64) and IgA (FcalphaRI, CD89), which are potent cytotoxic trigger molecules. Both receptors, however, require the FcR gamma chain for signaling. In this study, we show that FcgammaRI and FcalphaRI can trigger function independently of one another and do not cross-compete for the FcR gamma chain. FcalphaRI proved more efficient in initiating early signaling events and effector functions, such as redirected tumor cell killing and generation of superoxide. In addition, simultaneous engagement of FcgammaRI and FcalphaRI resulted in enhanced tumor cell lysis. These data support the development of concepts in which both FcgammaRI and FcalphaRI on PMN cells are targeted for tumor therapy.

Peptidoglycan and lipoteichoic acid modify monocyte phenotype in human whole blood

We examined the influence of the gram-positive cell wall products peptidoglycan (PepG) and lipoteichoic acid (LTA), compared to lipopolysaccharide (LPS), on the monocyte expression of receptors involved in antigen presentation (HLA-DR, B7.1, and B7.2), cell adhesion (intercellular adhesion molecule-1 [ICAM-1] and lymphocyte function associated antigen-3 [LFA-3]), phagocytosis (Fc gamma RI), and cell activation (CD14). We also evaluated possible influences of the immunosuppressive drugs cyclosporine A, tacrolimus, and sirolimus on the expression of these receptors. Pretreatment of whole blood for 4 h with the immunosuppressive drugs did not influence the expression of the surface receptors in normal or stimulated blood. Stimulation with both PepG and LTA caused significant up-regulation of the surface expression of ICAM-1 and HLA-DR on whole blood monocytes, similar to that obtained with LPS, whereas B7.1, B7.2, LFA-3, and Fc gamma RI were not modulated. PepG and LTA also caused increased expression of CD14, whereas LPS down-regulated this molecule. In contrast, we did not detect any significant influence of any of the bacterial products on the plasma concentration of soluble CD14. We hypothesized that the increased expression of surface CD14 in blood stimulated with PepG would prime for cellular activation by LPS. Indeed, we show that PepG and the partial PepG structure muramyl dipeptide acted in synergy with LPS to cause the release of tumor necrosis factor-alpha. The results suggest that PepG and LPS provoke partly different responses on monocyte phenotype and that CD14 may play different roles in the innate response to gram-positive and gram-negative bacteria.

Engineering of macrophages to produce IFN-gamma in response to hypoxia

Activation of murine macrophages (Mphi) requires the collaboration of signals derived from the immune system and the environment. In this study, we engineered a murine Mphi cell line to become activated in response to an environmental signal, hypoxia, as the sole stimulus. Hypoxia is a condition of low oxygen tension, occurring in several pathological tissues, which acts in synergy with IFN-gamma to induce full Mphi activation. We transfected the ANA-1 murine Mphi cell line with a construct containing the IFN-gamma gene controlled by a synthetic promoter inducible by hypoxia (HRE3x-Tk), and we characterized the cellular and molecular biology of the engineered Mphi under normoxia or hypoxia. Engineered Mphi in normoxia expressed basal levels of IFN-gamma mRNA and protein that were strongly augmented by shifting the cells to hypoxia. Furthermore, they responded to the synthesized IFN-gamma with induction of IFN-responsive factor-1 and 2'-5'-oligoadenylate synthase expression. Under normoxic conditions, the engineered Mphi had a significant constitutive level of Ia Ags and Fc receptors. Hypoxia induced further augmentation of Ia and Fc expression. Finally, hypoxia induced inducible NO synthase expression, and subsequent reoxygenation led to the production of NO. In conclusion, the engineered Mphi, which produce IFN-gamma in an inducible manner, express new biochemical and functional properties in response to low oxygen environment as the sole stimulus, thereby circumventing the need for costimulation by other immune system-derived signals.

Phenotypic and functional characterization of rhesus monkey decidual lymphocytes: rhesus decidual large granular lymphocytes express CD56 and have cytolytic activity

In this study, we carried out a phenotypic and functional characterization of lymphocytes isolated from the uterine endometrium of the pregnant rhesus monkey. A majority (80%) of these cells were CD56(bright+), CD3- had typical large granular lymphocyte/uterine natural killer (NK) cell morphology and contained numerous cytoplasmic granules. Flow cytometric evaluation showed that rhesus decidual CD56(bright+) cells shared other phenotypic features of human uterine NK cells, including low levels of CD45RA and CD62L expression. A majority of the rhesus uterine CD56(bright+) cells expressed low levels of CD 16 but were CD2-. In contrast, most rhesus CD16+ peripheral blood cells were CD56-. In addition to the primary population of CD56(bright+) cells, a minor subset of smaller and less granular CD56(intermediate+) decidual lymphocytes was identified, the majority of which were CD16-, CD2(+). Decidual CD56+ cells did not express monocyte/macrophage markers, including CD14, CD64 and CD68. Decidual lymphocytes effectively lysed K562, Raji and particularly 721.221 targets in cytotoxicity assays. Together, these results suggest that as in human pregnancy, rhesus decidual CD56(bright+) cells represent a distinct lymphocyte subset that belongs to the NK cell lineage.

Molecular fingerprint of interferon-gamma signaling in unstable angina

BACKGROUND

Activation of circulating monocytes in patients with acute coronary syndromes may reflect exposure to bacterial products or stimulation by cytokines such as IFN-gamma. IFN-gamma induces phosphorylation and nuclear translocation of transcription factor STAT-1, which initiates a specific program of gene induction. To explore whether monocyte activation is IFN-gamma driven, patients with unstable (UA) or stable angina (SA) were compared for nuclear translocation of STAT-1 complexes and upregulation of IFN-gamma-inducible genes CD64 and IP-10.

METHODS AND RESULTS

Peripheral blood mononuclear cells were stained for expression of CD64 on CD14(+) monocytes and analyzed by PCR for transcription of IP-10. Expression of CD64 was significantly increased in patients with UA. Monocytes from UA patients remained responsive to IFN-gamma in vitro, with accelerated transcriptional competency of CD64. IP-10-specific sequences were spontaneously detectable in 82% of the UA patients and 15% of SA patients (P<0.001). Most importantly, STAT-1 complexes were found in nuclear extracts prepared from freshly isolated monocytes of patients with UA, which provides compelling evidence for IFN-gamma signaling in vivo.

CONCLUSIONS

Monocytes from UA patients exhibit a molecular fingerprint of recent IFN-gamma triggering, such as nuclear translocation of STAT-1 complexes and upregulation of IFN-gamma-inducible genes CD64 and IP-10, which suggests that monocytes are activated, at least in part, by IFN-gamma. IFN-gamma may derive from stimulated T lymphocytes, which implicates specific immune responses in the pathogenesis of acute coronary syndromes.

The Fc receptor for IgG expressed in the villus endothelium of human placenta is Fc gamma RIIb2

To evaluate the potential role of human placental endothelial cells in the transport of IgG from maternal to fetal circulation, we studied Fc gamma receptor (Fc gamma R) expression by immunohistology and immunoblotting. Several pan-Fc gamma RII Abs that label the placental endothelium displayed a distribution pattern that correlated well with transport functions, being intense in the terminal villus and nil in the cord. In contrast, the MHC class 1-like IgG transporter, FcRn, and the classical Fc gamma RIIa were not expressed in transport-related endothelium of the placenta. Our inference, that Fc gamma RIIb was the likely receptor, we confirmed by analyzing purified placental villi, enriched in endothelium, by immunoblotting with a new Ab specific for the cytoplasmic tail of Fc gamma RIIb. These experiments showed that the Fc gamma RII expressed in villus endothelium was the b2 isoform whose cytoplasmic tail is known to include a phosphotyrosyl-based motif that inhibits a variety of immune responses. We suggest that this receptor is perfectly positioned to transport IgG although as well it may scavenge immune complexes.

MHC class I-related neonatal Fc receptor for IgG is functionally expressed in monocytes, intestinal macrophages, and dendritic cells

The neonatal Fc receptor (FcRn) for IgG, an MHC class I-related molecule, functions to transport IgG across polarized epithelial cells and protect IgG from degradation. However, little is known about whether FcRn is functionally expressed in immune cells. We show here that FcRn mRNA was identifiable in human monocytes, macrophages, and dendritic cells. FcRn heavy chain was detectable as a 45-kDa protein in monocytic U937 and THP-1 cells and in purified human intestinal macrophages, peripheral blood monocytes, and dendritic cells by Western blot analysis. FcRn colocalized in vivo with macrosialin (CD68) and Ncl-Macro, two macrophage markers, in the lamina propria of human small intestine. The heavy chain of FcRn was associated with the beta(2)-microglobulin (beta(2)m) light chain in U937 and THP-1 cells. FcRn bound human IgG at pH 6.0, but not at pH 7.5. This binding could be inhibited by human IgG Fc, but not Fab. FcRn could be detected on the cell surface of activated, but not resting, THP-1 cells. Furthermore, FcRn was uniformly present intracellularly in all blood monocytes and intestinal macrophages. FcRn was detectable on the cell surface of a significant fraction of monocytes at lower levels and on a small subset of tissue macrophages that expressed high levels of FcRn on the cell surface. These data show that FcRn is functionally expressed and its cellular distribution is regulated in monocytes, macrophages, and dendritic cells, suggesting that it may confer novel IgG binding functions upon these cell types relative to typical Fc gamma Rs: Fc gamma RI, Fc gamma RII, and Fc gamma RIII.

N-formyl-methionyl-leucyl-phenylalanine inhibits both gamma interferon- and interleukin-10-induced expression of FcgammaRI on human monocytes

Three different classes of receptors for the Fc portion of immunoglobulin G (FcgammaRs), FcgammaRI, FcgammaRII, and FcgammaRIII, have been identified on human leukocytes. One of them, FcgammaRI, is a high-affinity receptor capable of induction of functions that include phagocytosis, respiratory burst, antibody-dependent cell-mediated cytotoxicity (ADCC), and secretion of cytokines. This receptor is expressed on mononuclear phagocytes, and this expression is regulated by cytokines and hormones such as gamma interferon (IFN-gamma), IFN-beta, interleukin-10 (IL-10), and glucocorticoids. We have recently demonstrated that the chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine (FMLP) is capable of inducing a time-dependent downregulation of both FcgammaRIIIB and FcgammaRII in human neutrophils, altering FcgammaR-dependent functions. Considering the biological relevance of the regulation of FcgammaRI, we investigated the effect of FMLP on the overexpression of FcgammaRI induced by both IFN-gamma and IL-10 on human monocytes. We demonstrate that FMLP significantly abrogated IFN-gamma- and IL-10-induced FcgammaRI expression, although its basal level of expression was not altered. However, other IFN-gamma-mediated effects such as the overexpression of the major histocompatibility complex class II antigens and the enhancement of lipopolysaccharide-induced secretion of tumor necrosis factor alpha were not affected by FMLP treatment. The formyl peptide completely inhibited the IFN-gamma- and IL-10-induced enhancement of ADCC and phagocytosis carried out by adherent cells. The inhibitory effect of FMLP on FcgammaRI upregulation could exert an important regulatory effect during the evolution of bacterial infections.

Tumor cells express FcgammaRI which contributes to tumor cell growth and a metastatic phenotype

High levels of circulating immune complexes containing tumor-associated antigens are associated with a poor prognosis for individuals with cancer. The ability of B cells, previously exposed to tumor-associated antigens, to promote both in vitro and in vivo tumor growth formed the rationale to evaluate the mechanism by which immune complexes may promote tumor growth. In elucidating this mechanism, FcgammaRI expression by tumor cells was characterized by flow cytometry, polymerase chain reaction, and sequence analysis. Immune complexes containing shed tumor antigen and anti-shed tumor antigen Ab cross-linked FcgammaRI-expressing tumor cells, which resulted in an induction of tumor cell proliferation and of shed tumor antigen production. Use of selective tyrosine kinase inhibitors demonstrated that tumor cell proliferation induced by immune complex cross-linking of FcgammaRI is dependent on the tyrosine kinase signal transduction pathway. A selective inhibitor of phosphatidylinositol-3 kinase also inhibited this induction of tumor cell proliferation. These findings support a role for immune complexes and FcgammaRI expression by tumor cells in augmentation of tumor growth and a metastatic phenotype.