Expression of molecules involved in antigen presentation and T cell activation (HLA-DR, CD80, CD86, CD44 and CD54) by cultured human osteoblasts

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 molecule s in human osteoblasts. Methods: Human osteoblastic cells obtained from samples of normal bone obta ined during mandibular osteotomy were isolated, maintained in culture, and characterized. The identity of the cells was confirmed by their alkaline ph osphatase activity and their capacity to produce osteocalcin. Flow cytometr y was used to examine the expression HLA-DR, CD80, CD86, CD44, and CD54 mol ecules involved in immune activities. Results: We detected the expression of CD10, CD44, and HLA-DR antigens, mol ecules involved in antigen presentation in cultured osteoblastic cells. Alt hough the cells were negative for CD45, the leukocyte common antigen and CD 14 (an antigen detected on macrophages), they expressed CD54, CD80, and CD8 6 antigens, which are also involved in the mechanisms of antigen presentati on 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.