Immunophenotype of TStrC. TStrC displayed a MSC-like cell surface marker profile with negativity for markers of the hematopoietic system (CD34, CD45). CD56 - as a surface molecule expressed on most paediatric tumour cells - was negative in any case. All cell cultures were positive for the MSC markers CD73, CD90, CD105 (Fig. 3a). Dashed line: isotype control; bold line: antibody as indicated. Fig. 3b shows that a dim surface expression of HLA-DR could be found after a four day incubation period with 200 U/ml IFN-γ, which is present in most tumour environments (bold line TStrC in the presence of exogenous IFN-γ, dashed line control). The representative analysis was taken from tumour sample number 3.