Overview of Immune System

Abstract

Immune system refers to a unique and highly effective mechanism evolved in all the living organisms that resists, tolerates or controls the growth of foreign organisms inside the host. In addition to providing protection from foreign organisms, immune system also functions in identifying abnormal cells of the host such as cancer cells and prevents the development of cancers. In this chapter a detailed overview of immune system is presented. First the two different types of immune responses including innate and adaptive responses are introduced along with the details of differences between two types of responses. Innate immune response, which provides the immediate and first-line of defense, is then discussed with details on neutrophils, eosinophils, mast cells, basophils, natural killer cells and macrophages. Dendritic cells, which are critical for anti-cancer immune response, are discussed in a separate chapter. Complement system which plays an important role in innate immune response is also discussed in this chapter along with other innate immune cells. Next, the adaptive immune response, a highly evolved and target-specific defense against foreign organisms is discussed. While, adaptive immune response involves both T- and B-cells, B-cells are discussed in this chapter and T-cells are discussed in a separate chapter due to their significance in immunotherapy of cancer. The role of both innate and adaptive immune cells during cancer development is described and the mechanisms by which they support or oppose cancer progression is specially emphasized in this chapter.