Immunotherapy is a type of cancer treatment that harnesses the body's immune system to recognize and attack cancer cells. In the context of bladder cancer, immunotherapy has shown promising results, especially in cases where other treatments may not be as effective. The primary form of immunotherapy used for bladder cancer is immune checkpoint inhibitors.

Here's a basic overview of how immunotherapy works in treating bladder cancer:

1. **Immune Checkpoint Inhibitors:** The immune system has checkpoints that regulate its activity and prevent it from attacking normal cells. Cancer cells sometimes exploit these checkpoints to evade the immune system. Immune checkpoint inhibitors are drugs that block these checkpoints, allowing the immune system to recognize and attack cancer cells.

2. **PD-1/PD-L1 Inhibition:** One common target in bladder cancer immunotherapy is the PD-1/PD-L1 pathway. Programmed cell death protein 1 (PD-1) is a protein on the surface of immune cells, and programmed death-ligand 1 (PD-L1) is a protein on some cancer cells. When PD-1 on immune cells binds to PD-L1 on cancer cells, it can suppress the immune response. Immune checkpoint inhibitors that target PD-1 or PD-L1 can disrupt this interaction, allowing the immune system to attack the cancer cells.

3. **Activation of T Cells:** By blocking the inhibitory signals, immune checkpoint inhibitors activate T cells, a type of white blood cell, to recognize and destroy cancer cells. This helps the immune system to mount a more effective response against the bladder cancer.

4. **Durability of Response:** One of the advantages of immunotherapy is the potential for a durable response. In some cases, patients experience long-lasting benefits even after completing the treatment course, which may not be the case with some traditional forms of chemotherapy.

5. **Combination Therapies:** Researchers are also exploring combination therapies, where immunotherapy is used in conjunction with other treatments like chemotherapy or radiation. This approach aims to enhance the overall effectiveness of the treatment.

It's important to note that not all patients respond the same way to immunotherapy, and outcomes can vary. Additionally, there can be side effects associated with these treatments, as the immune system is stimulated to attack not only cancer cells but also normal cells. However, the overall goal is to provide a more targeted and less toxic approach to treating bladder cancer. The use of immunotherapy in bladder cancer is continually evolving as researchers conduct more clinical trials and gain a deeper understanding of its mechanisms and efficacy.