Generation and functional characterisation of canine bone marrow-derived macrophages

Chicken CSF2 and IL-4-, and CSF2-dependent bone marrow cultures differentiate into macrophages over time

Chicken bone marrow-derived macrophages (BMMΦ) and dendritic cells (BMDC) are utilized as models to study the mononuclear phagocytic system (MPS). A widely used method to generate macrophages and DC in vitro is to culture bone marrow cells in the presence of colony-stimulating factor-1 (CSF1) to differentiate BMMΦ and granulocyte-macrophage-CSF (GM-CSF, CSF2) and interleukin-4 (IL-4) to differentiate BMDC, while CSF2 alone can lead to the development of granulocyte-macrophage-CSF-derived DC (GMDC). However, in chickens, the MPS cell lineages and their functions represented by these cultures are poorly understood. Here, we decipher the phenotypical, functional and transcriptional differences between chicken BMMΦ and BMDC along with examining differences in DC cultures grown in the absence of IL-4 on days 2, 4, 6 and 8 of culture. BMMΦ cultures develop into a morphologically homogenous cell population in contrast to the BMDC and GMDC cultures, which produce morphologically heterogeneous cell cultures. At a phenotypical level, all cultures contained similar cell percentages and expression levels of MHCII, CD11c and CSF1R-transgene, whilst MRC1L-B expression decreased over time in BMMΦ. All cultures were efficiently able to uptake 0.5 µm beads, but poorly phagocytosed 1 µm beads. Little difference was observed in the kinetics of phagosomal acidification across the cultures on each day of analysis. Temporal transcriptomic analysis indicated that all cultures expressed high levels of CSF3R, MERTK, SEPP1, SPI1 and TLR4, genes associated with macrophages in mammals. In contrast, low levels of FLT3, XCR1 and CAMD1, genes associated with DC, were expressed at day 2 in BMDC and GMDC after which expression levels decreased. Collectively, chicken CSF2 + IL-4- and CSF2-dependent BM cultures represent cells of the macrophage lineage rather than inducing conventional DC.

Isolation and ex vivo characterization of the immunophenotype and function of microglia/macrophage populations in normal dog retina

Microglia are the primary resident immune cells of the retina and are involved in the pathogenesis of various retinal diseases. In this study, we optimized experimental conditions to isolate microglia from canine retinas and characterized ex vivo their immunophenotype and function using flow cytometry (FACS). The most suitable protocol included a mechanical dissociation of the retina and an enzymatic digestion using DNAse and collagenase. Extraction was carried out by density gradient centrifugation, and retinal microglia accumulated on distinct interfaces of 1.072 and 1.088 g/mL of a Percoll gradient. Immunophenotypical characterization was performed with monoclonal antibodies CD11b, CD11c, CD18, CD45, CD44, B7-1 (CD80), B7-2 (CD86), CD1c, ICAM-1 (CD54), CD14, MHCI, MHCII, CD68, CD3, CD4, CD8α, and CD21. The most prevalent microglia population in the normal canine retina is CD11b(high)CD45(low). Functionally, retinal microglia exhibited phagocytosis and reactive oxygen species (ROS) generation activities. To conclude, ex vivo examinations of retinal microglia are feasible and possibly reflect the in vivo conditions, avoiding artifacts observed in tissue culture. The established method will be relevant to examine microglia from diseased canine retinas in order to elucidate their roles in degenerative processes.

Suppression of canine myeloid cells by soluble factors from cultured canine tumor cells

BACKGROUND

Cancer profoundly affects immunity and causes immunosuppression that contributes to tumor escape, metastases and resistance to therapy. The mechanisms by which cancer cells influence immune cells are not fully known but both innate and adaptive immune cells can be altered by cancer. Myeloid cells are innate immune cells that comprise the mononuclear phagocytic system (MPS) and include monocytes, macrophages, dendritic cells (DCs) and their progenitors. Myeloid cells play important roles in both the promotion and regulation of immune responses. Dysregulated myeloid cells are increasingly being recognized as contributing to cancer-related immunosuppression. This study investigated whether soluble factors produced by canine tumor cells inhibited canine myeloid cell function.

METHODS

These studies investigated the utility of using the canine DH82 cell line for assessment of canine myeloid responses to tumor-derived soluble factors (TDSFs). Phenotypic comparisons to canine bone marrow-derived DCs (BM-DCs) and bone marrow-derived macrophages (BM-MΦs) were performed and expression of myeloid cell markers CD11b, CD11c, CD80, and major histocompatibility complex (MHC) class II were evaluated by flow cytometry. Phenotypic and functional changes of DC populations were then determined following exposure to tumor-conditioned media (TCM) from canine osteosarcoma, melanoma and mammary carcinoma cell lines.

RESULTS

We found that the canine BM-DCs and the DH82 cell line shared similar CD11b, CD11c and MHC II expression and morphologic characteristics that were distinct from canine BM-MΦs. Myeloid cells exposed to TDSFs showed decreased expression of MHC class II and CD80, had reduced phagocytic activity and suppressed the proliferation of responder immune cells.

CONCLUSION

These results show that soluble factors secreted from canine tumor cells suppress the activation and function of canine myeloid cells. Our results suggest that, similar to humans, dysregulated myeloid cells may contribute to immunosuppression in dogs with cancer.

A rapid and simple method to obtain canine peripheral blood-derived macrophages

Macrophages play an important role in a variety of situations, including pathogen elimination, inflammation, and tissue repair. However, these cells are not fully studied in dogs, in part, due to the difficulty of efficiently isolating and culturing them in vitro. In this study, we cultured canine peripheral blood mononuclear cells (PBMCs) with 10 ng/ml of phorbol 12-myristate-13-acetate (PMA) for 5 days to obtain macrophages. A high number of round-adherent cells were obtained without the addition of any cytokine. These cells showed active phagocytic activity and a cell surface antigen profile different from dendritic cells. Our method facilitates a high yield of macrophages in a short cultivation period compared with previous studies. This method might be a powerful tool to study macrophage functions in dogs.

In vitro binding and survival assays of Leishmania parasites to peripherical blood monocytes and monocyte-derived macrophages isolated from dogs naturally and experimentally infected with Leishmania (Leishmania) chagasi

BACKGROUND

There are a few works considering the characterization of canine monocyte-derived macrophages as well as a standardized procedure for isolation, culture, and infection of these cells with Leishmania. We have performed several modifications in order to improve the canine monocyte-derived macrophage cultures. In addition, we have done a comparative study between monocytes and monocyte-derived macrophages from dogs naturally and experimentally infected with L. chagasi.

RESULTS

In the presence of exogenous serum, opsonized Leishmania promastigotes binds better to monocytes/macrophages than without serum. Otherwise, this binding occurs due to the strict correlation between the opsonized biologic particles with the third receptor of the complement (CR3-CD11b/CD18). In fact, our assays with CD11b confirmed the importance of this receptor for canine cells and the L. chagasi experimental system. Moreover, monocytes obtained from naturally infected dogs have shown a higher number of monocytes bounded to promastigotes. The experimental results regarding survival have shown that promastigote forms of opsonized L. chagasi were more infective, because we found higher numbers of promastigotes bound to the different cells. As a consequence, after forty-eight hours of binding, higher numbers of amastigotes appeared inside monocyte-macrophages.

CONCLUSION

These studies have given support to continue comparative studies involving canine monocytes, monocyte-derived macrophages and peritoneal macrophages. Since we have standardized the canine cell culture, we are looking forward to determining the phenotypic properties of these cells before and after L. chagasi infection using flow cytometry.

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.

Canine long-term bone marrow culture neutrophil production and functionality

This in vitro study has been conducted to determine the optimal experimental conditions under which to produce canine neutrophils in long-term bone marrow cultures (LTBMC), establish functional parameters of neutrophils obtained from LTBMC and peripheral blood and to ascertain whether these cells display physiological similarities. Our aim is to provide an experimental model, enabling a correlation between hemopoietic injury and neutrophil functionality. The authors demonstrate for the first time that canine neutrophils grown in cultures are able to produce oxyradicals capable of killing bacterial products. Moreover, culture-grown neutrophils contain gelatinase granules, a marker of terminal neutrophil differentiation, and express a specific surface antigen. The results described in this article illustrate the development of a dynamic system that mimics physiological hemopoiesis.

Characterization of canine microglial cells isolated ex vivo

Microglia are the principal immune effector elements of the brain sharing immunophenotypic and functional characteristics of macrophages as well as of antigen presenting cells (APCs). The purpose of this study was to isolate canine microglial cells and make them available for ex vivo characterizations of their functions and immunophenotype. After isolation, carried out by density gradient centrifugation, microglial cells accumulated on distinct interfaces of 1.077 and 1.066 g/ml of a Percoll gradient. Identification of microglial cells in other species is realized by their specific immunophenotype of CD11b/c+ and CD45low. Our results indicate, that expression of CD45 is very low or even absent in canine microglial cells. In addition, they expressed CD18 and CD11b/c+, as determined by flow cytometry and immunohistochemistry. Fourteen additional monoclonal antibodies (mAbs) were used to characterize and compare canine microglial cells with monocytes. Microglia and monocytes can be clearly distinguished by their differential expression intensity of surface antigens (CD45, CD44, CD14). Functional characterization was assessed by a reactive oxygen species (ROS)-generation test and phagocytosis assay using flow cytometry. In conclusion, ex vivo examination of microglia is possible in dogs and most probably reflects the conditions in vivo. The measurement of tissue culture artifacts can be largely avoided using this method.

Generation and characterisation of an equine macrophage cell line (e-CAS cells) derived from equine bone marrow cells

Macrophages play a pivotal role in the pathophysiology of many diseases by mediating the host immune response to infections and intoxications. The species-specific activation of macrophages and the differential response in cytokine production impedes the extrapolation of results between species. Therefore, the aim of this study was to isolate and immortalise macrophages from equine bone marrow (BM) cells in order to study equine-specific signalling pathways. The isolated BM-derived macrophages (referred to as e-CAS cells) showed proliferation kinetics similar to that of standardised cell lines and were maintained in culture for >76 passages. To characterise the cells, a number of typical parameters of macrophages were tested. Morphological evaluation (May-Grünwald Giemsa staining) and non-specific esterase activity indicated the e-CAS cells to be macrophages. The presence of CD14 and their ability to phagocytose Escherichia coli bioparticles further confirmed their identity, as did their ability to produce cytokines, reactive oxygen and nitrogen intermediates in response to LPS. These data show that the established cell line (e-CAS) shows the characteristics of equine macrophages and may, therefore, prove to be a unique in vitro model for studying the cellular biology of equine inflammation.

Diagnosis of chronic myelogenous leukemia in a dog using morphologic, cytochemical, and flow cytometric techniques

Chronic myelogenous leukemia was diagnosed in a 3.5-year-old neutered male Golden Retriever. The diagnosis was based on persistent leukocytosis (>73.0X10(3)/microliter), composed of a proportionate left shift to progranulocytes with no evidence of underlying inflammation, infection, or neoplasia. Marked dysplasia was evident in neutrophils and platelets in peripheral blood. Bone marrow and splenic aspirates were dominated by mature and immature neutrophils with < 2% myeloblasts. Cytochemical and flow cytometric assays confirmed that cells in the peripheral blood and spleen were of committed neutrophil lineage. The dog responded initially to treatment with hydroxyurea, but developed acute undifferentiated leukemia approximately 83 days after initial presentation.