Innate (nonspecific) defenses: Guard against many types of pathogens; respond quickly, and Include species resistance, mechanical barriers, chemical barriers, natural killer
cells, inflammation, phagocytosis, and fever.
Use natural killer cells to defend the body against viruses and cancer cells by secreting cytolytic substances called perforins, which lyse (break apart) cell membranes of pathogens.
Phagocytosis: Engulfment and digestion of pathogens, foreign particles, and debris.