Levels of B7-2 in tumor cells of Hodgkin's disease.

T cell activation requires two signals: one is antigen-specific and controlled by major histocompatibility complex (MHC) proteins, the other is antigen-independent and primarily mediated through members of the B7 protein family. The tumor cells in classical Hodgkin's disease (cHD) express both MHC and B7 proteins, yet recognition of cHD tumor cells by T cells is inadequate. Quantitative analysis showed that tumor cells in cHD-involved tissue expressed similar levels of MHC II proteins as did antigen-presenting cells in reactive lymphoid tissue. In contrast, B7-2 levels were significantly lower in cHD tumor cells. These findings suggest that enhancing costimulatory signals might represent a promising therapeutic approach to overcome the poor immunogenicity observed in cHD tumor cells.