Phenotypic, functional, and quantitative characterization of canine peripheral blood monocyte-derived macrophages

The yield as well as phenotypic and functional parameters of canine peripheral blood monocyte-derived macrophages were analyzed. The cells that remained adherent to Teflon after 10 days of culture had high phagocytic activity when inoculated with Leishmania chagasi. Flow cytometric analysis demonstrated that more than 80% of cultured cells were positive for the monocyte/macrophage marker CD14.     

Dual tropism for macrophages and lymphocytes is a common feature of primary human immunodeficiency virus type 1 and 2 isolates.

We have investigated the ability of human immunodeficiency virus type 1 (HIV-1) and HIV-2 isolates to infect and replicate in primary human macrophages. Monocytes from blood donors were allowed to differentiate into macrophages by culture in the presence of autologous lymphocytes and human serum for 5 days before infection. A panel of 70 HIV-1 and 12 HIV-2 isolates were recovered from seropositive individuals with different severities of HIV infection. A majority of isolates (55 HIV-1 and all HIV-2) were obtained from peripheral blood mononuclear cells, but isolates from cerebrospinal fluid, monocytes, brain tissue, plasma, and purified CD4+ lymphocytes were also included. All isolates were able to infect monocyte-derived macrophages, even though the replicative capacity of the isolates varied. Interestingly, isolates with a rapid/high, syncytium-inducing phenotype did not differ from slow/low, non-syncytium-inducing isolates in their ability to replicate in monocyte-derived macrophages. Others have reported that rapid/high, syncytium-inducing isolates have a reduced ability to infect and replicate in monocytes. However, different methods to isolate and culture the monocytes/macrophages were used in these studies and our study. Thus, the ability of HIV isolates to replicate in monocytes/macrophages appears to be strongly influenced by the isolation and culture procedures. It remains to be determined which culture procedure is more relevant for the in vivo situation.     

Circulating CD2+ monocytes are dendritic cells

Low levels of CD2 have been described on subsets of monocytes, macrophages, and dendritic cells. CD2 is expressed on about one-third of circulating monocytes, at levels one-half log lower than on T or NK cells, representing 2-4% of PBMC. FACS analysis of CD2+ and CD2- monocytes revealed no significant difference in the expression of adhesion molecules (CD11a/b/c), class II Ags (HLA-DR, -DQ, -DP), myeloid Ags (CD13, CD14, CD33), or costimulatory molecules (CD80, CD86). Freshly isolated CD2+ and CD2- monocytes were morphologically indistinguishable by phase contrast microscopy. However, scanning electron microscopy revealed large prominent ruffles on CD2+ monocytes in contrast to small knob-like projections on CD2- monocytes. After 2 days of culture, the CD2+ monocytes largely lost CD14 expression and developed distinct dendrites, whereas the CD2- monocytes retained surface CD14 and remained round or oval. Freshly isolated CD2+ monocytes were more potent inducers of the allogeneic MLR and more efficiently induced proliferation of naive T cells in the presence of HIV-1 gp120 than did CD2- monocytes. After culture in the presence of GM/CSF and IL-4, CD2+ monocytes were up to 40-fold more potent than monocyte-derived dendritic cells or CD2- monocytes at inducing allogeneic T cell proliferation. These findings suggest that circulating CD2+ and CD2- monocytes are dendritic cells and the precursors of macrophages, respectively. Thus, dendritic cells are far more abundant in the blood than previously thought, and they and precursors of macrophages exist in the circulation as phenotypically, morphologically, and functionally distinct monocyte populations.     

Flow cytometry assessment of residual melanoma cells in tumor-infiltrating lymphocyte cultures

Adoptive transfer of tumor-infiltrating lymphocytes (TIL) is in development for the treatment of metastatic melanoma. In phase II clinical trials, patients with metastatic melanoma that received TIL after preconditioning had a 50-70% clinical response rate. The current approach to generate TIL is to culture melanoma enzyme digests in the presence of IL-2 for a 10- to 20-day period followed by 2 weeks of rapid expansion (REP). Prior to administration, cell therapies are characterized and tested for purity. TIL are characterized by CD3 surface marker expression, and purity is assessed by the amount of tumor remaining in culture. Evaluating TIL purity has traditionally been done by immunohistochemistry, which is often considered semiquantitative. To generate a quantitative assay, we used multiparameter flow cytometry to evaluate the presence of viable tumor cells by staining TIL populations with a viability dye and an antibody cocktail that detects intracellular tumor-antigens gp100, Mart-1, tyrosinase, S100, and surface tumor-antigen melanoma chondroitin sulfate proteoglycan (MCSP), and CD3 on T cells. Tumors were identified by gating on the viable CD3(-) population. Antigens in tumors were initially optimized with individual antibodies using both immunohistochemistry and flow cytometry. When eight different tumor cell lines were spiked into an activated T cell culture, flow cytometry was able to distinguish lymphocytes from tumors in all samples tested. Most importantly, the assay was able to detect melanoma cells in all enzyme digests (9/9) from patient samples. After IL-2-induced TIL expansion, there was a significant decrease in tumor cells; tumor cells were detected in only 2 of 12 samples. In eight IL-2-induced TIL samples that were further expanded in REP, no tumor cells were detected. We have demonstrated that flow cytometry is an alternative to immunohistochemistry for defining the purity of a TIL population.     

De novo Generation of Cells within Human Nurse Macrophages and Consequences following HIV-1 Infection

Nurse cells are defined as those that provide for the development of other cells. We report here, that in vitro, human monocyte-derived macrophages can behave as nurse cells with functional capabilities that include de novo generation of CD4+ T-lymphocytes and a previously unknown small cell with monocytoid characteristics. We named these novel cells "self-renewing monocytoid cells" (SRMC), because they could develop into nurse macrophages that produced another generation of SRMC. SRMC were not detectable in blood. Their transition to nurse behavior was characterized by expression of CD10, a marker of thymic epithelium and bone marrow stroma, typically absent on macrophages. Bromodeoxyuridine labeling and immunostaining for cdc6 expression confirmed DNA synthesis within nurse macrophages. T-cell excision circles were detected in macrophages, along with expression of pre-T-cell receptor alpha and recombination activating gene 1, suggesting that genetic recombination events associated with generation of the T-cell receptor were occurring in these cells. SRMC expressed CCR5, the coreceptor for R5 HIV-1 isolates, and were highly susceptible to HIV-1 entry leading to productive infection. While expressing HIV-1, SRMC could differentiate into nurse macrophages that produced another generation of HIV-1-expressing SRMC. The infected nurse macrophage/SRMC cycle could continue in vitro for multiple generations, suggesting it might represent a mechanism whereby HIV-1 can maintain persistence in vivo. HIV-1 infection of nurse macrophages led to a decline in CD4+ T-cell production. There was severe, preferential loss of the CCR5+ CD4+ T-cell subpopulation. Confocal microscopy revealed individual HIV-1-expressing nurse macrophages simultaneously producing both HIV-1-expressing SRMC and non-expressing CD3+ cells, suggesting that nurse macrophages might be a source of latently infected CD4+ T-cells. Real-time PCR experiments confirmed this by demonstrating 10-fold more HIV-1-genome-harboring T-cells, than virus-expressing ones. These phenomena have far-reaching implications, and elicit new perspectives regarding HIV pathogenesis and T-cell and hematopoietic cell development.     

Infectious HIV-1 assembles in late endosomes in primary macrophages

Although human immunodeficiency virus type 1 (HIV-1) is generally thought to assemble at the plasma membrane of infected cells, virions have been observed in intracellular compartments in macrophages. Here, we investigated virus assembly in HIV-1-infected primary human monocyte-derived macrophages (MDM). Electron microscopy of cryosections showed virus particles, identified by their morphology and positive labeling with antibodies to the viral p17, p24, and envelope proteins, in intracellular vacuoles. Immunolabeling demonstrated that these compartments contained the late endosomal marker CD63, which was enriched on vesicles within these structures and incorporated into the envelope of budding virions. The virus-containing vacuoles were also labeled with antibodies against LAMP-1, CD81, and CD82, which were also incorporated into the viral envelope. To assess the cellular source of infectious viruses derived from MDM, virus-containing media from infected cells were precipitated with specific antibodies. Only antibodies against antigens found in late endosomes precipitated infectious virus, whereas antibodies against proteins located primarily on the cell surface did not. Our data indicate that most of the infectious HIV produced by primary macrophages is assembled on late endocytic membranes and acquires antigens characteristic of this compartment. This notion has significant implications for understanding the biology of HIV and its cell-cell transmission.     

Bacterial adhesion, intracellular survival and cytokine induction upon stimulation of mononuclear cells with planktonic or biofilm phase Staphylococcus epidermidis

Staphylococcus epidermidis is a leading cause of hospital-acquired and biofilm-associated infections. Interactions of peripheral blood mononuclear cells (PBMCs) and monocyte-derived macrophages with planktonic or biofilm phase S.?epidermidis cells were studied. Biofilm phase bacteria exhibited higher attachment, as well as, a 10-fold higher intracellular survival in monocyte-derived macrophages than their planktonic counterparts. Stimulation of PBMCs and monocyte-derived macrophages was performed with live or formalin-fixed bacterial cells. Supernatant concentration of selected cytokines was measured by Luminex(?) xMAP(?) technology at different time points. As compared to planktonic phase, biofilm phase bacteria elicited lower amounts of proinflammatory cytokines and Th1 response cytokines, such as TNFα, IL-12p40, IL-12p70 and IFN-γ, whereas they enhanced production of IL-8, GM-CSF and IL-13. This phenomenon was independent of formalin pretreatment. Taken together, these results may contribute to interpretation of observed silent course of biofilm-associated infections.     

Recombinant human (rh) stem cell factor and rhIL-4 stimulate differentiation and proliferation of CD3+ cells from umbilical cord blood and CD3+ cells enhance FcepsilonR1 expression on fetal liver-derived mast cells in the presence of rhIL-4

We previously reported that rhIL-4 induced apoptosis and rhIL-6 mediated protection of human mast cells derived from cord blood mononuclear cells. Based on the result, we attempted to obtain the phenotypes and differentiation of CD3+ cells from cord blood by investigating their cell surface markers in the presence of rhSCF plus rhIL-4. The effect of co-cultured CD3+ cells on fetal liver mast cells (FLMCs) was also determined. Phenotypes from cord blood-derived cells were analyzed by flow cytometry and cell numbers were determined. Fetal liver mast cells were cultured with cord blood-derived cells (mainly CD3+) in the presence of rhSCF and/or rhIL-4 and were analyzed to determine cell number and expression of Kit+ and FcepsilonR1. The percentage of CD3+ cells from cord blood-derived cells on day 0 was about 41 +/- 13.5%, following monocytes and granulocytes. CD3+ cells increased in number (1.5-fold) and purity (90%), whereas other cell types did not survive. More than 60% of CD3+ cells from cord blood at day 0 were CD4(-)CD8-. These double-negative cells dramatically decreased by 1 week of culture, while CD4+CD8+ cells increased in number and purity through 3 weeks of culture, and then decreased as greater numbers of single-positive T cells emerged. We also found that FcepsilonR expression on FLMC increased in the presence of rhIL-4, but was not affected by the T cells that developed from cord blood mononuclear cells. The results indicate that IL-4, a Th2 type cytokine, together with rhSCF, can induce T cell proliferations, differentiation, and maturation from cord blood progenitor cells.     

Marker profile for the evaluation of human umbilical artery smooth muscle cell quality obtained by different isolation and culture methods

Even though umbilical cord arteries are a common source of vascular smooth muscle cells, the lack of reliable marker profiles have not facilitated the isolation of human umbilical artery smooth muscle cells (HUASMC). For accurate characterization of HUASMC and cells in their environment, the expression of smooth muscle and mesenchymal markers was analyzed in umbilical cord tissue sections. The resulting marker profile was then used to evaluate the quality of HUASMC isolation and culture methods. HUASMC and perivascular-Wharton’s jelly stromal cells (pv-WJSC) showed positive staining for α-smooth muscle actin (α-SMA), smooth muscle myosin heavy chain (SM-MHC), desmin, vimentin and CD90. Anti-CD10 stained only pv-WJSC. Consequently, HUASMC could be characterized as α-SMA+ , SM-MHC+ , CD10? cells, which are additionally negative for endothelial markers (CD31 and CD34). Enzymatic isolation provided primary HUASMC batches with 90–99 % purity, yet, under standard culture conditions, contaminant CD10+ cells rapidly constituted more than 80 % of the total cell population. Contamination was mainly due to the poor adhesion of HUASMC to cell culture plates, regardless of the different protein coatings (fibronectin, collagen I or gelatin). HUASMC showed strong attachment and long-term viability only in 3D matrices. The explant isolation method achieved cultures with only 13–40 % purity with considerable contamination by CD10+ cells. CD10+ cells showed spindle-like morphology and up-regulated expression of α-SMA and SM-MHC upon culture in smooth muscle differentiation medium. Considering the high contamination risk of HUASMC cultures by CD10+ neighboring cells and their phenotypic similarities, precise characterization is mandatory to avoid misleading results.     

Role of the basic domain of human immunodeficiency virus type 1 matrix in macrophage infection.

The matrix domain of the human immunodeficiency virus type 1 (HIV-1) Gag protein contains a highly basic region near its amino terminus. It has been proposed that this basic domain, in conjunction with the HIV-1 accessory protein Vpr, is responsible for the localization of the HIV-1 preintegration complex to the nucleus in nondividing cells. It has also been postulated that the matrix basic domain assists in the targeting of the HIV-1 Gag precursor Pr55Gag to the plasma membrane during virus assembly. To evaluate the role of this highly basic sequence during infection of primary human monocyte-derived macrophages, single- and double-amino-acid-substitution mutations were introduced, and the effects on virus particle production, Gag protein processing, envelope glycoprotein incorporation into virus particles, and virus infectivity in the CEM(12D-7) T-cell line, peripheral blood mononuclear cells, and primary human monocyte-derived macrophages were analyzed. Although modest effects on virus particle production were observed with some of the mutants, none abolished infectivity in primary human monocyte-derived macrophages. In contrast with previously reported studies involving some of the same matrix basic domain mutants, infectivity in monocyte-derived macrophages was retained even when combined with a vpr mutation.     

A Simple and Efficient Method to Isolate Macrophages from Mixed Primary Cultures of Adult Liver Cells

Kupffer cells are liver-specific resident macrophages and play an important role in the physiological and pathological functions of the liver^1-3. Although the isolation methods of liver macrophages have been well-described^4-6, most of these methods require sophisticated equipment, such as a centrifugal elutriator and technical skills. Here, we provide a novel method to obtain liver macrophages in sufficient number and purity from mixed primary cultures of adult rat liver cells, as schematically illustrated in Figure 1.After dissociation of the liver cells by two-step perfusion method^7,8,a fraction mostly composed of parenchymal hepatocytes is prepared and seeded into T75 tissue culture flasks with culture medium composed of DMEM and 10% FCS.Parenchymal hepatocytes lose the epithelial cell morphology within a few days in culture, degenerate or transform into fibroblast-like cells (Figure 2). As the culture proceeds, around day 6, phase contrast-bright, round macrophage-like cells start to proliferate on the fibroblastic cell sheet (Figure 2). The growth of the macrophage-like cells continue and reach to maximum levels around day 12, covering the cell sheet on the flask surface. By shaking of the culture flasks, macrophages are readily suspended into the culture medium. Subsequent transfer and short incubation in plastic dishes result in selective adhesion of macrophages(Figure 3), where as other contaminating cells remain suspended. After several rinses with PBS, attached macrophages are harvested. More than 10⁶ cells can be harvested repeatedly from the same T75 tissue culture flask at two to three day intervals for more than two weeks(Figure 3).The purities of the isolated macrophages were 95 to 99%, as evaluated by flow cytometry or immunocytochemistry with rat macrophage-specific antibodies (Figure 4).The isolated cells show active phagocytosis of polystylene beads (Figure 5), proliferative response to recombinant GM-CSF, secretion of inflammatory/anti-inflammatory cytokines upon stimulation with LPS, and formation of multinucleated giant cells⁹.In conclusion, we provide a simple and efficient method to obtain liver macrophages in sufficient number and purity without complex equipment and skills.This method might be applicable to other mammalian species.     

Mature dendritic cells derived from human monocytes within 48 hours: a novel strategy for dendritic cell differentiation from blood precursors

It is widely believed that generation of mature dendritic cells (DCs) with full T cell stimulatory capacity from human monocytes in vitro requires 5-7 days of differentiation with GM-CSF and IL-4, followed by 2-3 days of activation. Here, we report a new strategy for differentiation and maturation of monocyte-derived DCs within only 48 h of in vitro culture. Monocytes acquire immature DC characteristics by day 2 of culture with GM-CSF and IL-4; they down-regulate CD14, increase dextran uptake, and respond to the inflammatory chemokine macrophage inflammatory protein-1alpha. To accelerate DC development and maturation, monocytes were incubated for 24 h with GM-CSF and IL-4, followed by activation with proinflammatory mediators for another 24 h (FastDC). FastDC expressed mature DC surface markers as well as chemokine receptor 7 and secreted IL-12 (p70) upon CD40 ligation in the presence of IFN-gamma. The increase in intracellular calcium in response to 6Ckine showed that chemokine receptor 7 expression was functional. When FastDC were compared with mature monocyte-derived DCs generated by a standard 7-day protocol, they were equally potent in inducing Ag-specific T cell proliferation and IFN-gamma production as well as in priming autologous naive T cells using tetanus toxoid as a model Ag. These findings indicate that FastDC are as effective as monocyte-derived DCs in stimulating primary, Ag-specific, Th 1-type immune responses. Generation of FastDC not only reduces labor, cost, and time required for in vitro DC development, but may also represent a model more closely resembling DC differentiation from monocytes in vivo.     

Effect of culture and maturation on human monocyte-derived dendritic cell surface markers,necrosis and antigen binding

Abstract

Dendritic cells (DC) are antigen-presenting cells (APC) that are important for innate and acquired immune responses. Owing to their involvement in autoinflammation, autoimmunity and cancer, DC are useful cellular models for biomedical research. Appropriate DC production in vitro could aid the study of DC in many human diseases. We used fluorochrome-based flow cytometry assays to analyze the effects of culture period and maturation of monocyte-derived DC (MoDC) on their viability and necrosis, purity, CD11c expression and phagocytic capacity. The morphological changes that occur as purified monocytes become DC were assessed at 24 and 72 h, and 6 and 9 days in culture. The dynamics of certain cell surface markers of monocytes and mature MoDC (mMoDC) also were assessed using fluorescence-based assays. We found that day 6 of culture yielded the most functional immature MoDC (iMoDC) with maximal viability, purity, CD11c expression and appropriate phagocytic capacity. Mass production of viable MoDC could be useful for immunotherapy.     

Streptococcal preparation OK432 promotes functional maturation of human monocyte-derived dendritic cells

Streptococcal preparation OK432 is an immunomodulatory agent extensively used as adjuvant therapy for gastric cancer in Japan. OK432 augments the cytotoxic activity of various effector cells such as lymphocytes, macrophages and (natural killer) NK cells and induces the production of multiple cytokines. Dendritic cells (DC) are professional antigen-presenting cells (APC) that can be used for cancer vaccine therapy. In the present study, we investigated the effect of OK432 on the activation of DC. Here we report that OK432 induced phenotypic and functional maturation of human monocyte-derived DC. In vitro culture of immature DC generated from adherent peripheral blood mononuclear cells (PBMC) using granulocyte macrophage-colony stimulating factor (GM-CSF) and interleukin-4 (IL-4) with OK432 at various doses (0.01 to 0.1 KE/ml) for 2 days resulted in increased cell surface expression of CD80, CD83, CD86 and ICAM-1 in a dose-dependent manner. The expression of CD83, a selective marker of mature DC, on DC activated by OK432 (OK-DC) was maximally enhanced after 3 days of incubation. Assay of cytokine production in OK-DC after 2 days in culture revealed that OK432 was a strong inducer of IL-12 and interferon-gamma (IFN-gamma). OK432 efficiently augmented the primary allogeneic T-cell responses by DC. This distinct phenotypic profile and allostimulatory capacity of OK-DC was stable for at least 48 h of additional culture in the absence of any cytokines. Moreover, the antiviral cytotoxic T lymphocytes (CTL) response in vitro was also enhanced by the addition of OK432 to the cultures. These findings suggest that OK432 is a potent stimulator of DC, and that stimulated DC are strong inducers of the T helper 1 (Th1)-type response. We conclude that OK-DC are likely candidates for use as an adjuvant for DC-based cancer immunotherapy.     

Differential expression of CD14, CD36 and the LDL receptor on human monocyte-derived macrophages

 Macrophages are key players in many aspects of human physiology and disease. It has been hypothesized that in a given microenvironment monocytes differentiate into specific subpopulations with distinct functions. In order to study the role of macrophage heterogeneity in atherogenesis, we established a novel isolation and culture technique for human monocyte-derived macrophages. The present technique does not select for monocyte subpopulations prior to the onset of differentiation. Monocytes were cultured for 2 weeks in the presence of autologous lymphocytes before being plated quantitatively. They differentiated into mature macrophages in terms of morphology, lipid composition, and biological activity. Based on phagocytic activity as well as on the expression of CD14, CD36, and the low-density lipoprotein (LDL) receptor, we have identified macrophage subpopulations that may play distinct roles in atherogenesis. While virtually all adherence-purified monocytes expressed CD14, CD36, and the LDL-R, we characterized three subpopulations of macrophages based on the expression of these antigens: CD36⁺CD14^–LDL-R^– (58±12%), CD36⁺CD14⁺LDL-R⁺(18±5%), the remaining cells being CD36^–CD14^–LDL-R^–. The first two subsets decreased in size during further differentiation (51±12% and 8±3%, respectively). Our culture technique may also serve as a good model for studying the implications of macrophage heterogeneity in diseases other than atherosclerosis. Accepted: 13 February 1998     

Cytotoxic activity against maedi-visna virus-infected macrophages.

The cell type predominantly infected by maedi-visna virus (MVV) is the macrophage, and we have looked at the ability of MVV-infected macrophages to interact with cytotoxic T lymphocytes (CTL), important effector cells against virus infections. MVV-specific CTL precursors were detected, after in vitro culture with MVV antigen and recombinant human interleukin-2, in peripheral blood lymphocytes of all MVV-infected sheep. MVV-infected monocyte-derived macrophages and alveolar macrophages were able to stimulate CTL activity in vitro and were targets for these activated CTL. The major effector cell population using MVV-infected macrophage targets was CD8+ lymphocytes, although another population, lymphokine-activated killer cells, may also have been involved. There was no direct cytotoxic activity found in alveolar lymphocytes from MVV-infected sheep without lung lesions.     

Dys-regulation of effector CD4+ T cell function by the V3 domain of the HIV-1 gp120 during antigen presentation.

It was recently demonstrated that the semiconserved domain of the V3 region of the HIV-1 surface glycoprotein gp120 can induce an activation-apoptosis phenomenon to memory CD4+ cells from healthy individuals. Studying the effects of V3 on the interaction of antigen presentation between monocyte-derived macrophages and resting memory CD4+ T cells, we observed that V3 affects both cell populations. Macrophages exposed to composite liposomes containing V3 on the surface and tetanus toxoid (TT) as the recall antigen entrapped in the aqueous phase (lipoV3/TT liposomes) were able to activate CD4+ T cells during primary stimulation, but not after restimulation nine days later. Unstimulated macrophages or macrophages exposed to soluble TT responded to second stimuli, lipoV3/TT liposomes, and soluble TT in activating CD4+ T cells. Soluble TT-activated CD4+ T cells could be restimulated by soluble TT but not by lipoV3/TT liposomes, whereas lipoV3/TT liposome-activated CD4+ T cells became unresponsive to a second stimulus. These results show that resting memory CD4+ cells activated by macrophages presenting the recall antigen together with V3 become unresponsive to restimulation.