The innate immune system employs three primary strategies to distinguish between self and nonself: recognition of microbial nonself, recognition of missing self, and recognition of induced or altered self. Recognition of microbial nonself involves the detection of conserved molecular patterns unique to microorganisms, such as lipopolysaccharide (LPS) and peptidoglycan, which are recognized by pattern recognition receptors (PRRs) to trigger an immune response. Recognition of missing self relies on the detection of markers of normal self, such as major histocompatibility complex (MHC) class I proteins, which are recognized by inhibitory receptors to prevent the immune system from attacking healthy cells. Recognition of induced or altered self involves the detection of markers that indicate cellular stress or infection, such as CD47 and human MICA, which signal for assisted apoptosis or phagocytosis by immune cells. These strategies ensure that the immune system can effectively defend against pathogens while minimizing harm to the host's own tissues.The innate immune system employs three primary strategies to distinguish between self and nonself: recognition of microbial nonself, recognition of missing self, and recognition of induced or altered self. Recognition of microbial nonself involves the detection of conserved molecular patterns unique to microorganisms, such as lipopolysaccharide (LPS) and peptidoglycan, which are recognized by pattern recognition receptors (PRRs) to trigger an immune response. Recognition of missing self relies on the detection of markers of normal self, such as major histocompatibility complex (MHC) class I proteins, which are recognized by inhibitory receptors to prevent the immune system from attacking healthy cells. Recognition of induced or altered self involves the detection of markers that indicate cellular stress or infection, such as CD47 and human MICA, which signal for assisted apoptosis or phagocytosis by immune cells. These strategies ensure that the immune system can effectively defend against pathogens while minimizing harm to the host's own tissues.