'Immune surveillance' without immunogenicity.

The hypothesis of immune surveillance against cancer is based on two premises; (1) that transformed and normal cells generally have different antigenic qualities, and (2) that the immune system responds to the antigenically modified cells in essentially the same way as it responds to invasive microorganisms. Both premises have been questioned. Here, Zvi Grossman and Ronald Herberman suggest that lymphoid cells not only mediate immune responses but also assist in regulating the differentiation of a variety of normal cells. They do so by recognizing self rather than foreign antigens. By forcing and steering the turnover of tissue cells, lymphoid cells prevent the accumulation of small irregular phenotypic and karyotypic changes in the tissue. Tumor escape from surveillance may therefore be described as escape from regulatory differentiation pressures.