Defective
Immunity
Hypothesis - The rate of spontaneous mutations is much greater than the observed frequency of tumours. From this it can be concluded that:
(i) there must be some mechanism for suppression mutations resulting in cancer, or
(ii) the newly formed cancer cells must be destroyed in some way.
It is now believed that the latter possibility, is correct. Newly formed cancer cells are destroyed by the immunological responses of the cell.
This is called immunological surveillance. Cancerous cells have been found to contain antigens not found in ordinary cells
