Immunosuppression and Human Malignancy

The immune system can deal effectively with the majority of viruses and bacteria, less effectively with parasites, and very poorly with cancer. Why is this so? Why are McFarlane Burnet's and Lewis Thomas' predictions that the immune system is in­ volved in ridding the body of cancer cells, encapsulated in the catchy phrase "immunologic surveillance," so difficult to experi­ mentally establish? Cancer differs from infectious agents in being derived from the host. Hence, it has been postulated that cancer cells lack anti­ gens that the immune system can recognize. They are not "im­ munogenic. " However, this argument is seriously weakened by the existence of numerous human autoimmune diseases, in which the immune system effectively recognizes and attacks a va­ riety of self tissues. Thus, the potential clearly exists for recogni­ tion of the surfaces of tumor cells. Professor Naor and his colleagues have written a book that explores another possible reason: cancer cells are recognized by the immune system-but is it possible that the consequence of recognition is inhibition of the immune system-by suppressor T cells or macrophages? The evolution of the malignant state may only occur in individuals who develop this suppression. This book reviews the evidence that suppressor cells, poorly characterized and difficult to study, may be of fundamental im­ portance in cancer. In fact, our incapacity to understand the na­ ture of suppressor cells and their mode of action is one of the ma­ jor problems in immunology research today.

Induction of Suppressor Cells by Immunostimulants.- 1. Introduction.- 2. Induction of Suppressor Cells by BCG.- 3. Induction of Suppressor Cells by C. parvum and Other Immunostimulants.- 4. Conclusions.- Control of Natural Killer Cells by Suppressor Cells.- 1. Introduction.- 2. Activity of Anti-NK Suppressor Cells in Normal Animals.- 3. Activation of Anti-NK Suppressor Cells by Irradiation or Treatment with Estrogen.- 4. Activation of Anti-NK Suppressor Cells by External Stimulators.- 5. Activity of Anti-NK Suppressor Cells in TBH.- 6. Mechanisms.- 7. Suppression or Artifact?.- 8. Suppressor Cells Controlling NK-Cell Activity in Human Beings.- Antigenic Entities of the Tumor That Induce Suppressor Cells May Prevent the Potentiation of Coexpressed Immunogenic Entities.- Suppressor Cells in Human Malignant Diseases.- 1. Introduction.- 2. Hodgkin's Disease.- 3. Non-Hodgkin's Lymphomas, Leukemias, and Multiple Myelomas.- 4. Cancer of the Head and Neck.- 5. Lung Cancer.- 6. Alimentary-Tract Malignancies.- 7. Genitourinary Malignancies.- 8. Gynecologic Malignancies.- 9. Cancer of the Breast.- 10. Melanoma and Other Skin Malignancies.- 11. Malignancies of the Central Nervous System.- 12. Some Considerations of the Role of Immune Suppression in Human Malignancy.- 13. The Effect of Antineoplastic Chemotherapy on Human Suppressor-Cell Activity.- Suppressor Cells and Malignancy in Animal Experimental Models: A Brief Summary of Recent Findings.- 1. Suppressor Macrophages and "Null" Cells.- 2. "Sneaking Through" of Low Doses of Tumor Cells Is Mediated by Suppressor Cells.- 3. Suppressor T Cells and Their Mechanism of Action.- 4. Suppressor T Cell Lines and Clones.- 5. Suppression of Concomitant Immunity.- 6. Immunotherapy Based on Suppressor Cells Eradication.- 7.Immunoregulation of Antitumor Autoimmunity by Suppressor T Cells.- General Conclusions.- References.