Summarize this : The immune system is characterized by its ability to mount defenses against pathogens through innate and adaptive responses. The innate immune response is the first line of defense and operates from the moment of exposure to pathogens. It includes physical and chemical barriers such as skin, mucous membranes, and gastric acids. Should these barriers be breached, the second line of defense involves internal processes such as phagocytic cells like neutrophils and macrophages, dendritic cells, and natural killer cells, which respond to pathogens in a generic, non-specific manner (Parker et al., 2016). In contrast, the adaptive immune response constitutes the third line of defense and is characterized by its specificity and memory. It is slower to activate compared to the innate response but provides a tailored response against specific pathogens. The adaptive response includes lymphocytes such as T cells and B cells, which recognize specific antigens via receptors. Once activated, these cells proliferate and differentiate into effector cells that target the pathogen directly or by producing antibodies, and memory cells that remain in the body to provide quicker responses upon re-exposure to the same pathogen. In summary, the innate immune system provides a broad and immediate defense against