Human osteoblast-like cells expressing MHC class II determinants stimulate allogeneic and autologous peripheral blood mononuclear cells and function as antigen-presenting cells.

We have previously shown that a subset of human osteoblast-like bone surface cells (HBC) derived from explants of trabecular bone constitutively express class II major histocompatibility complex (MHC) determinants in long-term culture. We now examine the capacity of HBC to stimulate allogeneic and autologous peripheral blood mononuclear cells (PBMC) and to function as antigen-presenting cells (APC). HBC consistently stimulated a strong proliferative response in allogeneic PBMC after 6 days co-culture. Stimulation of autologous PBMC was weaker and less consistent. HBC and adherent PBMC were equally active in stimulating a PPD response in autologous non-adherent PBMC. These observations suggest that immune cells initiated by HBC may play a role in normal and disordered bone remodelling processes.