Isolation of cultured human monocytes/macrophages in suspension utilizing liquid and solid phase gelatin

Gelatin positively regulates the immunosuppressive capabilities of adipose-derived mesenchymal stem cells

This characteristics of adipose-derived mesenchymal stem cells (Ad-MSCs) can be selectively enhanced by altering the culture environment. We evaluated the effects of gelatin on Ad-MSCs when used in combination with culture media. Ad-MSCs were initially cultured in 0%, 0.5%, 1%, 2%, and 4% gelatin in Dulbecco's modified Eagle's medium (DMEM) to evaluate cell proliferation. This expression of inflammatory, antiinflammatory, antioxidant, and osteogenic markers was then assessed by rtPCR in Ad-MSCs cultured in 0.5% gelatin in DMEM (GMSCs), and without gelatin (MSCs), for 5 and 10 days. We found that 0.5% gelatin significantly increased the proliferation rate of Ad-MSCs after 24 h of incubation, up until 72 h. GMSCs had upregulated IL-10, VEGF, and HO-1 after 5 and 10 days of incubation, while IL-6 and TNF-α were upregulated after 5 days and then significantly decreased after 10 days of incubation. The osteogenic factors BMP-7, AXIN, and β-catenin were significantly upregulated in GMSCs after 5 and 10 days. Notably, there was 5- to 8-fold higher expression of BMP-7 in GMSCs than in MSCs. We conclude that culture medium containing 0.5% gelatin enhances the proliferation rate, induces immunosuppression, and activates BMP-7 and the wnt/AXIN/β-catenin pathway in Ad-MSCs.

Kinetics of human myeloid-derived suppressor cells after blood draw

Background

Human myeloid-derived suppressor cells (MDSC) have been described as a group of immature myeloid cells which exert immunosuppressive action by inhibiting function of T lymphocytes. While there is a huge scientific interest to study these cells in multiple human diseases, the methodological approach varies substantially between published studies. This is problematic as human MDSC seem to be a sensible cell type concerning not only cryopreservation but also time point after blood draw. To date data on delayed blood processing influencing cell numbers and phenotype is missing. We therefore evaluated the kinetics of granulocytic MDSC (gMDSC) and monocytic MDSC (mMDSC) frequencies after blood draw in order to determine the best time point for analysis of this recently defined cell type.

Methods

In this study, we isolated peripheral blood mononuclear cells (PBMC) of patients with HIV infection or solid tumors directly after blood draw. We then analyzed the frequencies of gMDSC and mMDSC 2, 4 and 6 h after blood draw and after an overnight rest by FACS analysis using the standard phenotypic markers. In addition, part of the cells was frozen directly after PBMC preparation and was measured after thawing.

Results

gMDSC levels showed no significant difference using fresh PBMC over time with a limitation for the overnight sample. However they were massively diminished after freezing (p = 0.0001 for all subjects). In contrast, frequencies of fresh mMDSC varied over time with no difference between time point 2 and 4 h but a significantly reduction after 6 h and overnight rest (p = 0.0005 and p = 0.005 respectively). Freezing of PBMC decreased the yield of mMDSC reaching statistical significance (p = 0.04). For both MDSC subgroups, FACS analysis became more difficult over time due to less sharp divisions between populations.

Conclusions

According to our data human MDSC need to be studied on fresh PBMC. gMDSC can be studied with delay, mMDSC however should be studied no later than 4 h after blood draw. These results are crucial as an increasing number of clinical trials aim at analyzing MDSC nowadays and the logistics of blood processing implies delayed sample processing in some cases.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-015-0755-y) contains supplementary material, which is available to authorized users.

Membrane interactions involved in the induction of interferon-alpha by Mycoplasma pneumoniae

Interferon (IFN) induction by Mycoplasma pneumoniae (MP) in human peripheral blood mononuclear cells (PBMC) has been studied. We show that IFN yields depend on the concentration of both lymphocytes and MP. The effective IFN inducer appears to be the mycoplasma membrane, and IFN production occurs without significant lymphocyte proliferation. Data obtained by both positive and negative selection experiments suggest that the PBMC subpopulation induced by MP is B lymphocyte, as opposed to the main subpopulation induced by NDV that is monocyte. Evidence is also provided suggesting that the membrane interaction between MP and the B cells is mediated by MHC Class II antigens.

Purification of human monocytes on gelatin-coated surfaces

Human peripheral blood monocytes secrete a cell membrane-associated glycoprotein, cold insoluble globulin (fibronectin). Since fibronectin binds to gelatin-coated surface, we developed a simple technique for separation of human peripheral blood monocytes from whole mononuclear cell preparation. These preparations are characterized by a high monocyte purity (more than 90%), low platelet contamination and excellent viability.

Monoclonal antibodies against human Ia antigens stimulate monocytes to secrete interleukin 1

The monoclonal antibodies (mAb) DA6.147, DA6.164, and HIG.48 against human Ia antigens, but not the W6/32 mAb against human class I major histocompatibility complex antigens or the anti-monocyte OKM1 and 63D3 mAb, stimulated monocytes to secrete interleukin 1 (IL-1). IL-1 was measured by its property of promoting the production of interleukin 2 (IL-2) by phytohemagglutinin-treated LBRM-33 clone 1A5 cells. IL-1 activity induced by anti-Ia antibodies could be detected 24 hr after initiation of the cultures and reached its highest levels at days 3-4 of culture. Concentrations of 1 microgram/ml or higher of the anti-Ia antibodies induced monocytes to secrete significant levels of IL-1 activity. The anti-Ia mAb induced Ia-bearing but not Ia-negative monocytes to secrete IL-1. Both Ia-positive and Ia-negative monocytes produced IL-1 activity under the stimulus of lipopolysaccharide. It is concluded that the DA6.147, DA6.164, and HIG.48 mAb stimulate secretion of IL-1 by interacting Ia antigens on monocytes. The data support the view that besides serving as restricting elements for recognition of foreign antigens by T cells, Ia antigens may also function as transducer elements.

Cathepsin B activity in human blood monocytes during differentiation in vitro

The activity of cathepsin B was assayed in human blood monocytes during differentiation into macrophages in vitro. Freshly isolated monocytes showed negligible cathepsin B activity. On day 3 in culture the enzyme activity was still very low, but it was markedly increased on day 7, concomitant with the monocytes' morphological differentiation into tissue macrophage-like cells. A further rise in enzyme activity was seen on day 10 in culture. Acid phosphatase activity showed similar, but less marked, increases in human monocytes during 10 days' culture. Generally, higher enzyme levels were seen in monocytes isolated from buffy coat preparations than from whole blood. Both the level and the rate of appearance of cathepsin B activity were further enhanced by endocytosis of carrageenan in the monocytes. Stimulation with endotoxin from Escherichia coli caused variable enzyme responses, as certain pools of human cells expressed cathepsin B activity compared with controls, whereas others showed no change in activity. Endocytosis of carrageenan had no effect on acid phosphatase activity, whereas stimulation with endotoxin led to increased levels of this enzyme activity in all cultures. The present data suggest that a rise in cathepsin B activity may be a component in the differentiation of human monocytes into macrophages. They further indicate separate regulation of lysosomal enzyme activity in human monocytes after some types of stimulation, as previously shown for mouse macrophages.