The expression and detection of MHC class I antigens on murine neuroblastoma and ependymoblastoma lines

It has been reported that human neuroblastoma lines are almost devoid of class I transplantation antigens, while human glioma lines express these antigens. Other studies have also shown a paucity of class I antigens on the murine neuroblastoma line N2A, and the expression of these antigens by the murine ependymoblastoma G26 lines. Such differences might represent heterogeneity in class I antigen expression by different brain cell types, and the importance of this to the immunology of the brain prompted us to re-examine class I expression by these cell lines in more detail. Using an exhaustive number of approaches, we were not able to detect significant differences in class I surface antigen expression between N2A and the G26 lines. We compared the murine neuroblastoma line Cl300 and its cloned derivative, N2A, to the lines G26-20 and G26-24. Antibody-dependent, complement-mediated cytotoxicity revealed detectable levels of both K and D region antigens on these lines. Immunocytofluorometric analysis further confirmed that these lines express high levels of class I antigens, although due to their large sizes, the surface densities of class I antigens on these cells are lower than splenocytes. This lower density of class I molecules did not impede the capacity of either the neuroblastoma or the G26 lines to serve as targets of H-2K- or D-specific T effectors. Finally, comparison of these two cell types for class I RNA transcripts also revealed no difference. Thus, our findings which are the most detailed study of these lines are drastically different from findings in humans as well as earlier findings in the murine system. Likely explanations are discussed and precautions are given for the study of class I antigen expression by these lines.