Introduction: Tumor and the Host Immune System

Cancer is not one simple disease but a group of heterogeneous diseases sharing a common feature of uncontrolled cell growth. Cancer is a leading health issue in modern society and patients succumb to the disease every day. Among many different treatment approaches, harnessing the immune system to treat cancer has gained prominence in recent years. While some of the cancer cells can evade the host immune surveillance as well as spread distally, the majority of cancer cells are removed from the host immune system in premalignant stages of the disease. Accumulating evidence indicates that the host immune system is highly involved in the elimination of cancer cells, but ultimately, cancer cells have developed their own mechanisms to subvert the immune system. A comprehensive understanding of the immune system and its interaction with cancer is crucial to develop immune-based treatments. The currently available cancer immunotherapies are developed from a systemic understanding of the human immune system. This opening chapter will serve as an introductory remark to briefly summarize the human immune system, cancer and both positive and negative interactions between the immune system and cancer.

Keywords: Adaptive immunity, antibody, antigen, B cell, B cell receptor, cancer, cancer-associated antigen, costimulatory molecules, cytokine, dendritic cell (DC), hematopoietic stem cell (HSC), immune system, immunoglobulin, immunotherapy, innate immunity, myeloid cells, major histocompatibility complex (MHC), natural killer (NK) cell, T cell, T cell receptor (TCR).