Major CD14 Research Articles

Identification of a human progenitor strictly committed to monocytic differentiation: a counterpart of mouse cMoPs

Monocytes give rise to macrophages and dendritic cells (DCs) under steady-state and inflammatory conditions, thereby contributing to host defense and tissue pathology. Inflammation triggers the differentiation of tissue-infiltrating monocytes into monocyte-derived macrophages and DCs, which are associated with homeostatic host defense reactions and inflammatory diseases. In mice, monocytes are divided into classical Ly6chi- and non-classical Ly6clo-expressing subsets. Ly6clo monocytes are present only in the blood; however, Ly6chi monocytes are found in blood and other tissues (wherein they differentiate into macrophages and DCs). In this context, most Ly6clo monocytes are derived from Ly6chi monocytes. In humans, monocytes comprise major CD14+CD16- and other CD14+CD16+ and CD14loCD16+ monocytes. A monocyte lineage-restricted common monocyte progenitor (cMoP) was previously identified in mice; herein, we introduce human cMoP, which was identified as a CLEC12AhiCD64hi subpopulation of conventional granulocyte-monocyte progenitors (cGMPs) in umbilical cord blood and bone marrow. The human cMoP produced monocyte subsets without showing any potential of differentiating into myeloid or lymphoid cells ex vivo. Within the cGMP population, we also identified revised GMPs that completely lacked DC and lymphoid potential, which sequentially produced cMoPs, pre-monocytes, and monocytes. Collectively, our findings enhance the current understanding of human myeloid cell differentiation pathways.

Peritoneal macrophage heterogeneity is associated with different peritoneal dialysis outcomes

Peritonitis remains the major obstacle for the maintenance of long-term peritoneal dialysis and dysregulated host peritoneal immune responses may compromise local anti-infectious defense, leading to treatment failure. Whilst, tissue mononuclear phagocytes, comprising macrophages and dendritic cells, are central to a host response to pathogens and the development of adaptive immune responses, they are poorly characterized in the human peritoneum. Combining flow cytometry with global transcriptome analysis, the phenotypic features and lineage identity of the major CD14+ macrophage and CD1c+ dendritic cell subsets in dialysis effluent were defined. Their functional specialization was reflected in cytokine generation, phagocytosis, and antigen processing/presentation. By analyzing acute bacterial peritonitis, stable (infection-free) and new-starter patients receiving peritoneal dialysis, we identified a skewed distribution of macrophage to dendritic cell subsets (increasing ratio) that associated with adverse peritonitis outcomes, history of multiple peritonitis episodes, and early catheter failure, respectively. Intriguingly, we also noted significant alterations of macrophage heterogeneity, indicative of different maturation and activation states that were associated with different peritoneal dialysis outcomes. Thus, our studies delineate peritoneal dendritic cells from macrophages within dialysate, and define cellular characteristics associated with peritoneal dialysis treatment failure. These are the first steps to unravelling the detrimental adaptive immune responses occurring as a consequence of peritonitis.

Phenotypic and functional analysis of monocyte populations in cattle peripheral blood identifies a subset with high endocytic and allogeneic T-cell stimulatory capacity.

Circulating monocytes in several mammalian species can be subdivided into functionally distinct subpopulations based on differential expression of surface molecules. We confirm that bovine monocytes express CD172a and MHC class II with two distinct populations of CD14+CD16low/-CD163+ and CD14−CD16++CD163low- cells, and a more diffuse population of CD14+CD16+CD163+ cells. In contrast, ovine monocytes consisted of only a major CD14+CD16+ subset and a very low percentage of CD14−CD16++cells. The bovine subsets expressed similar levels of CD80, CD40 and CD11c molecules and mRNA encoding CD115. However, further mRNA analyses revealed that the CD14−CD16++ monocytes were CX3CR1highCCR2low whereas the major CD14+ subset was CX3CR1lowCCR2high. The former were positive for CD1b and had lower levels of CD11b and CD86 than the CD14+ monocytes. The more diffuse CD14+CD16+ population generally expressed intermediate levels of these molecules. All three populations responded to stimulation with phenol-extracted lipopolysaccharide (LPS) by producing interleukin (IL)-1β, with the CD16++ subset expressing higher levels of IL-12 and lower levels of IL-10. The CD14−CD16++ cells were more endocytic and induced greater allogeneic T cell responses compared to the other monocyte populations. Taken together the data show both similarities and differences between the classical, intermediate and non-classical definitions of monocytes as described for other mammalian species, with additional potential subpopulations. Further functional analyses of these monocyte populations may help explain inter-animal and inter-species variations to infection, inflammation and vaccination in ruminant livestock.

Peripheral Blood CD14high CD16+ Monocytes are Main Producers of IL‐10

Based on CD14 and CD16 expression, human peripheral blood monocytes (MO) can be divided into a major CD14(high) CD16(-) population and two minor CD14(high) CD16(+) and CD14(dim) CD16(+) subpopulations. CD14(dim) CD16(+) MO are well characterized and regarded as pro-inflammatory because upon stimulation produce TNF-alpha but little, if any, IL-10. By contrast, little is known about CD14(high) CD16(+) MO. We investigated the surface expression of selected determinants by CD16(+) MO subpopulations, cytokine production, phagocytosis and antigen presentation. We found that both CD16(+) subpopulations had a higher expression of HLA-DR, CD86, CD54 and a lower expression of CD64 than CD14(high) CD16(-) population. In addition, CD14(high) CD16(+) MO showed a higher expression of CD11b and TLR4 than CD14(dim) CD16(+) and CD14(high) CD16(-) subpopulations. CD14(high) CD16(+) MO exhibited an increased phagocytic activity and a decreased antigen presentation in comparison with CD14(dim) CD16(+). As expected, lipopolysaccharide (LPS)-stimulated CD14(dim) CD16(+) MO produced TNF-alpha but little IL-10. By contrast, LPS-stimulated CD14(high) CD16(+) subpopulation produced significantly more IL-10 than CD14(dim) CD16(+) and CD14(high) CD16(-) MO. In conclusion, our data show that human peripheral blood CD16(+) MO are heterogeneous in function and consist of two subpopulations: CD14(dim) CD16(+) pro-inflammatory and CD14(high) CD16(+) with anti-inflammatory potential.

The Monocyte/IgE Connection: May Polymorphisms in the CD14 Gene Teach Us about IgE Regulation?

Background: Total IgE levels are known to be under genetic control. Linkage studies have indicated that one or more loci on chromosome 5q may control total IgE, as well as asthma and bronchial hyperresponsiveness to nonspecific stimuli. Our group has undertaken a systematic analysis of chromosome 5q, and has recently characterized five single nucleotide polymorphisms at position –1619, –1359, –1145, –809 and –159 in the promoter of the gene encoding CD14, the myeloid pattern recognition receptor that is critical for efficient innate immune response to lipopolysaccharide (LPS) and bacterial ligands. Methods: Carriers of the major CD14 haplotypes were analyzed for serum levels of IgE and soluble CD14. In vitro IgE synthesis was assessed in peripheral blood mononuclear cells stimulated with IL-4 in the presence or absence of LPS or anti-CD14 monoclonal antibodies. Results: An inverse correlation was found between serum levels of IgE and soluble CD14. On the other hand, in vitro IL-4-dependent IgE synthesis was strongly upregulated by LPS, but suppressed by anti-CD14 monoclonal antibodies. Conclusions: Our results highlight the complex role played by monocytes in IgE regulation.

CD14: a bridge between innate immunity and adaptive IgE responses

Total IgE levels are known to be under genetic control. Linkage studies have indicated that one or more loci on chromosome 5q may control total IgE, as well as asthma and bronchial hyperresponsiveness to non-specific stimuli. Our group has undertaken a systematic analysis of chromosome 5q, and has recently characterized five single nucleotide polymorphisms at position -1619, -1359, -1145, -809, and -159 in the promoter of the gene encoding CD14, the myeloid pattern recognition receptor that is critical for efficient innate immune responses to lipopolysaccharide and bacterial ligands. Individuals homozygous for the three major CD14 haplotypes found in the Children Respiratory Study population (n = 390) were analyzed for serum levels of total IgE and soluble CD14. A strong inverse correlation was found between these two parameters, i.e. carriers of the -1359T/-1145A/-159C haplotype had the highest levels of IgE, and the lowest levels of sCD14. Conversely, carriers of the -1359G/-1145G/-159T haplotype had the highest levels of sCD14 and the lowest IgE values. Our results suggest that genetic variation in CD14, a key gene of innate immunity, may modulate the effects that exposure to bacterial ligands has on the development of Th2 responses.