What is Immune Rejection?
Immune rejection is a biological process where the immune system recognizes and attacks cells it identifies as foreign or abnormal. In the context of cancer, this can mean the immune system targeting and destroying cancerous cells. However, the relationship between cancer and the immune system is complex and multifaceted.
How Does the Immune System Recognize Cancer Cells?
The immune system uses
MHC molecules to present antigens on the surface of cells. Cancer cells often present abnormal antigens that can be recognized by
T cells and other immune components. When these antigens are identified as non-self, the immune system can initiate an attack to destroy the cancerous cells.
Downregulation of MHC molecules, making it harder for T cells to recognize them.
Secretion of immunosuppressive molecules like
TGF-beta and
IL-10.
Creation of a
tumor microenvironment that is hostile to immune cells.
Expression of immune checkpoint molecules such as
PD-L1, which inhibit T cell activity.
What are Immune Checkpoint Inhibitors?
Immune checkpoint inhibitors are a class of drugs designed to block proteins that prevent T cells from attacking cancer cells. By inhibiting these checkpoints, such as PD-1/PD-L1 or
CTLA-4, these drugs can enhance the body's immune response against cancer.
Pembrolizumab and
Nivolumab are examples of such inhibitors.
What is Tumor Immunoediting?
Tumor immunoediting is the process by which the immune system interacts with cancer cells, leading to their elimination, equilibrium, or escape. This process involves three phases:
Elimination: The immune system detects and destroys cancer cells.
Equilibrium: A state where cancer cells are held in check by the immune system but not completely eliminated.
Escape: Cancer cells evade the immune system and grow unchecked.
What are Cancer Vaccines?
Cancer vaccines aim to stimulate the immune system to attack cancer cells by presenting cancer-specific antigens. These vaccines can be either preventive or therapeutic. An example of a preventive cancer vaccine is the
HPV vaccine, which prevents cervical cancer. Therapeutic vaccines, such as
Sipuleucel-T, are designed to treat existing cancers.
Heterogeneity of tumors, which makes it difficult for the immune system to target all cancerous cells.
Development of resistance mechanisms by cancer cells.
Immune-related adverse effects due to overstimulation of the immune system.
The need for personalized treatment approaches.
Conclusion
Immune rejection holds great promise for cancer treatment, but significant challenges remain. Advances in immunotherapy, including immune checkpoint inhibitors, cancer vaccines, and adoptive cell transfer, offer new hope. Ongoing research aims to better understand and overcome the mechanisms by which cancer evades immune detection, potentially leading to more effective therapies in the future.
