In Article <34tjd6$755 at jhunix1.hcf.jhu.edu>, ejf at welchlink.welch.jhu.edu (Ephraim Fuchs) wrote: >I do not believe in immunosurveillance because tumors arise from cell >types that cannot provide a costimulatory signal for naive T cell >activation. What about B-cell lymphomas and melanomas (which express B7, see P. Hersey et al in latest Intl. J. Cancer)???