The book Immune Response Activation is aiming to analyse the multifaceted aspects of the immune response, treating a number of representative cases in which the immune response is, on one hand, activated against pathogens, and, on the other hand, involved in pathologic settings, leading to allograft rejection, allergy and autoimmunity. The regulatory mechanisms in which the immune response can be modulated for rendering its effector components more efficient and/or not harmful to the organism is also dissected in translational purposes in cancer immunotherapy, local immunity against bacteria and viruses, as well as in allergy and autoimmunity.