How does the immune system fight Cancer

Cancer cells are compared to a car with DNA as the driver's seat. DNA has 'brakes' (tumor-suppressing genes) and an 'accelerator' (oncogenes). Damage from UV light, chemicals, heavy metals, or genetics can affect these. Our cells fix most daily damage, but over time, mutations accumulate, leading to cancer, which is why it's often diagnosed later in life. Damaged tumor-suppressing genes allow cells to divide faster, potentially leading to benign tumors. Damaged oncogenes accelerate cell growth, leading to full-blown cancer which can metastasize.

The immune system fights cancer with specific cells, primarily CD8 T cells and natural killer (NK) cells. CD8 T cells are long-lived, activated by infections and vaccinations, and identify cancer cells by checking their 'ID' (MHC Class 1). If a cancer cell's ID looks suspicious and there's a 'co-stimulatory factor' (danger signal) present, the CD8 T cell destroys it using perforin (punching holes) and granzyme (initiating cell death). They also release tumor necrosis factor (TNF) to kill cancer cells.

Natural killer cells also check IDs but are more aggressive. If a cell completely lacks an ID, NK cells destroy it using perforin and granzyme. They can also initiate cell death through direct binding via the 'fast ligand' receptor. Both CD8 T cells and NK cells are crucial in eliminating pre-cancerous cells.

Cancer cells employ various tactics to hide from the immune system. They release immunosuppressive cytokines like IL-10 and TGF-beta, which 'put to sleep' immune cells. They can also remove their 'ID tags' (MHC Class 1) to avoid CD8 T cells; however, this makes them targets for natural killer cells. The worst-case scenario is when cancer cells retain their ID but hide the co-stimulatory factor, leading CD8 T cells to mistakenly identify them as safe and no longer target them.

Chemotherapy works by destroying cancer cell DNA, but it also affects healthy, rapidly dividing cells, causing side effects like hair loss. Immunotherapy aims to boost the immune system's ability to fight cancer. It can increase the presentation of MHC Class 1 and co-stimulatory molecules on cancer cells, making them more visible to CD8 T cells. Additionally, immunotherapy can alter the cytokine environment, replacing immunosuppressive signals with pro-inflammatory ones like TNF-alpha to enhance cancer destruction.