Search

Background/aims: Osteoblasts are classically considered to play an important role during bone tissue development, and to be involved in the formation of mineralized bone matrix. Recent reports have suggested that they can also exert some activities directly associated with the immune system (cytokine synthesis and antigen presentation). Moreover, some authors have found antigens on osteoblast-like cells normally expressed by other cells with a common origin in bone marrow., Methods: We isolated and cultured human osteoblast-like lines and studied their antigenic phenotype with flow cytometry using monoclonal antibodies against antigens associated with hematopoietic cells., Results: Cultured cells expressed CD34, but were negative for CD45. B cell antigens CD20 and CD23 and myelomonocytic antigens CD11b, CD13, and CD16 were detected. Expression of CD3, CD14, CD15 and CD68 was negative, whereas CD25 expression was positive. CD56, an antigen expressed on NK cells, was positive. These cells were CD10, CD44, CD54, CD80, CD86 and HLA-DR positive, as previously described. An antigen specific to follicular dendritic cells was also observed on cultured osteoblast-like cells., Conclusions: The antigenic phenotypes of human osteoblast-like cells and FDC are similar. These data suggest that osteoblasts may be functionally related to certain dendritic cells and may play an additional role in bone tissue to that classically assigned., (Copyright 2002 S. Karger AG, Basel)

Decidual stromal cells (DSC) are the main cellular component of the human decidua, but thus far their ascription to a given cell lineage is uncertain. In previous studies, these cells have been isolated and maintained in culture, and their antigen phenotype has been analysed to determine their affiliation. However, the presence in the culture medium of high proportions of fetal calf serum (FCS) may inhibit the expression of some surface antigens. In the present study, we show by flow cytometry that CD34 is rapidly down-regulated in human DSC cultured in RPMI 1640 with 20% FCS. For this reason, we used fibroblast medium, which contains only a small proportion (2%) of FCS, to isolate and culture these cells. Under these conditions DSC exhibited a stable antigen phenotype highly similar to that of these cells in vivo. Flow cytometry results confirmed that DSC cultured in fibroblast medium expressed CD34 protein, and reverse transcription-polymerase chain reaction findings showed that they have CD34 mRNA. Decidual stromal cells were also positive for STRO-1, an antigen that identifies stromal precursors of the bone marrow which also expresses CD34. The expression of CD10, CD13, alkaline phosphatase and alpha-smooth muscle actin by DSC, and the absence of expression of CD14 and CD45, further confirmed their relationship with the stromal precursors.

Background: Osteoblasts express the CD44 antigen and HLA class II antigens, molecules which, together with other costimulatory molecules such as CD80, CD86, and CD54, are involved in antigen presentation and T cell activation. The aim of this study was to investigate the expression of these molecules in human osteoblasts., Methods: Human osteoblastic cells obtained from samples of normal bone obtained during mandibular osteotomy were isolated, maintained in culture, and characterized. The identity of the cells was confirmed by their alkaline phosphatase activity and their capacity to produce osteocalcin. Flow cytometry was used to examine the expression HLA-DR, CD80, CD86, CD44, and CD54 molecules involved in immune activities., Results: We detected the expression of CD10, CD44, and HLA-DR antigens, molecules involved in antigen presentation in cultured osteoblastic cells. Although the cells were negative for CD45, the leukocyte common antigen and CD14 (an antigen detected on macrophages), they expressed CD54, CD80, and CD86 antigens, which are also involved in the mechanisms of antigen presentation to and activation of T cells., Conclusions: Our results suggest that osteoblastic cells or a subpopulation of these cells may have immune functions in bone. Further studies in which immune functions are assessed will be needed to test this hypothesis.

We previously reported that decidual stromal cells (DSC) from early human decidua express antigens associated with hematopoietic cells and develop different immune functions. Here we study the antigenic phenotype of DSC from term decidua and compare it with the phenotype reported for DSC from early decidua. Decidual stromal cells were isolated from human term deciduas and maintained in culture until highly purified DSC cultures were obtained. Most term DSC, like most early DSC, expressed CD10. Term DSC expressed antigens specific for follicular dendritic cells (FDC), such as DRC-1 (CD21L) and HJ2, together with CD21, CD23 and CD80, which are detected on FDC as well. Also like early DSC, term DSC were negative for CD3, CD14, CD15 and CD45. Although early DSC were reported to be HLA-DR-positive and CD86-positive, these antigens were not expressed by term DSC. These discrepant results suggest that two types of cells, or cells at different stages of differentiation (decidualization) were selected during culture of decidual cells from different periods of gestation. This possibility was further supported by the finding that term DSC expressed desmin and prolactin, two markers of decidualization, whereas these molecules have not previously been detected in early DSC.

The origin and function of decidual stromal cells (DSC), the main cellular component of the decidua, are uncertain. Although the general consensus is that they are fibroblastic cells involved in fetal trophoblast nutrition, several authors have demonstrated that these cells can carry out immunological functions and that at least a subpopulation of them may be of hematopoietic origin. Human DSC precursors or predecidual cells (preDSC) purified by expansion in culture express a surface phenotype recalling that of dendritic cells. In the present study, we show by flow cytometry that these cells also express B7-1 (CD80) and B7-2 (CD86), two antigens involved in the costimulation of T cells by antigen-presenting cells. Cultured DSC were also able to stimulate allogenic T cells in vitro. Using an immunohistochemical technique, we found that in cryostatic sections of early human decidua, CD80 and CD86 were expressed mainly by DSC located around the decidual vessels, a location compatible with preDSC rather than fully differentiated DSC. Our results suggest that preDSC are involved in antigen presentation.