Innate Immunity: Non-specific Defenses
The innate immune response is rapid and antigen-independent
Innate immunity, the body’s first line of defense, is non-specific and activates independently of antigens, allowing for the rapid identification and elimination of foreign threats.1 Numerous cell types are involved with the innate immune response, including macrophages, neutrophils, dendritic cells, mast cells, basophils, eosinophils, natural killer (NK) cells, and lymphocytes (T cells).1 The primary effector cells of the innate immune response, NK cells, continually scan the body for abnormal cells to attack.1-3 NK cells do not rely on antigens to identify nonself invaders.1 Instead, NK cells express receptors that interact with activating and inhibitory signals from normal and abnormal cells. The balance of these signals determines NK cell behavior.4 By engaging inhibitory receptors on NK cells, normal cells are able to identify themselves as self and protect against immune attack.5 In contrast, tumor cells express ligands that are not typical of normal cells.2,6 When the activating signals of tumor ligands prevail, they stimulate NK cell antitumor immunity.5,7
NK cells are part of the first line of defense against cancer
Upon recognition of a tumor cell through engagement of an activating receptor, NK cells proliferate and rapidly kill their target.3,8 Following tumor cell death, the NK cells move on, in search of other targets.3 In death, tumor cells can release tumor antigens, which can stimulate an adaptive immune response.9,10
References
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