Natural immunity definition
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Understanding Natural Immunity: Definition and Mechanisms
Definition of Natural Immunity
Natural immunity refers to the body's inherent ability to resist infections and diseases through pre-existing defense mechanisms. This type of immunity is present from birth and does not require previous exposure to pathogens or antigens to be effective. It is a non-specific first line of defense that operates immediately or within hours of an antigen's appearance in the body 14.
Components of Natural Immunity
Innate Immune Response
The innate immune response is a crucial component of natural immunity. It includes physical barriers like the skin and mucous membranes, as well as immune cells such as macrophages, neutrophils, and natural killer (NK) cells. These cells are pre-programmed to recognize and eliminate pathogens through mechanisms like phagocytosis and cytotoxicity 48. NK cells, for instance, are known for their ability to destroy virus-infected cells and tumor cells without prior sensitization .
Natural Antibodies
Natural antibodies (NAbs) are another vital element of natural immunity. These antibodies are present in the body before any exposure to specific antigens. They provide an immediate response to infections, allowing time for the adaptive immune system to generate a more specific response. NAbs are produced by B cells and play multiple roles in the immune system, including the neutralization of pathogens and the activation of other immune cells .
Mechanisms of Action
Pathogen Recognition and Elimination
Natural immunity involves the recognition and elimination of pathogens through various mechanisms. Immune cells like macrophages and neutrophils identify and engulf pathogens, while NK cells induce apoptosis in infected or abnormal cells 48. The innate immune system also triggers inflammatory responses to contain and eliminate infections .
Role of Bioactive Compounds
Certain bioactive compounds from natural sources, such as plants and fungi, can enhance natural immunity. These compounds, including polyphenols, terpenoids, and β-glucans, have immunomodulatory properties that boost the activity of immune cells like macrophages and NK cells. They also possess antimicrobial, antioxidant, and anti-inflammatory properties, which help in preventing cell damage and supporting overall immune function .
Natural Immunity vs. Acquired Immunity
Natural Immunity
Natural immunity is the body's inherent defense mechanism that does not require prior exposure to pathogens. It is always active and provides immediate protection against a wide range of infections 14.
Acquired Immunity
In contrast, acquired immunity develops after exposure to specific pathogens or through vaccination. It involves the production of specific antibodies and memory cells that provide long-term protection against future infections by the same pathogen. Acquired immunity can be further classified into naturally acquired immunity (e.g., immunity developed after recovering from an infection) and artificially acquired immunity (e.g., immunity developed through vaccination) 36.
Conclusion
Natural immunity is a fundamental aspect of the immune system, providing immediate and non-specific defense against infections. It involves various components, including innate immune responses and natural antibodies, which work together to recognize and eliminate pathogens. Understanding the mechanisms of natural immunity and its distinction from acquired immunity is crucial for developing effective strategies to enhance immune function and prevent diseases.
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