Hybrid cells formed by fusion of Epstein-Barr virus-associated B-lymphoblastoid cells and either marrow-derived or solid tumour-derived cell lines display different co-stimulatory phenotypes and abilities to activate allogeneic T-cell responses in vitro

Abstract

A panel of stable cell hybrids was generated by fusing a range of marrow-derived and solid tumour-derived human cell lines with the B-lymphoblastoid cell lines, HMy2 or KR4, and expression of immunologically relevant accessory and co-stimulatory molecules, and ability to stimulate allogeneic T-cell responses in vitro was investigated. Hybrid cell lines generated from three marrow-derived tumour cells consistently expressed both MHC class I and class II molecules, a range of accessory and T-cell co-stimulatory ligand molecules, including CD80 and CD86, and directly stimulated markedly enhanced T-cell proliferative responses in vitro, as compared with the parent tumour cell lines. The responses were blocked by addition of CTLA4-Ig fusion protein to the cultures, indicating a role of CD28/B7 interaction in induction of T-cell activation. By contrast, hybrid cells derived from three solid tumours only expressed MHC class II when the parent tumour cell line expressed MHC class II and consistently failed to express CD80 or CD86. These hybrid cells also stimulated greater T-cell proliferative responses in vitro than the parent tumour cell lines, although effective co-stimulation depended on the presence of responder non-T cells in the cultures. The expression of co-stimulatory ligand molecules and ability to directly stimulate strong allogeneic T-cell responses correlated with the EBV latency type of the hybrid cells. These data suggest that phenotypic and functional differences in fusion cells of professional antigen- presenting cells and tumour cells arise as a result of the parent tumour cell type.