immuun

Immuun describes the state of being resistant to disease or the functioning of the immune system, the network of cells, tissues, and molecules that defend the body against pathogens and malignant cells. The immune system recognizes foreign substances, or antigens, and initiates responses to neutralize or remove them while limiting damage to the body's own tissues. Immunity can be natural or acquired: natural immunity arises from biology and exposure, while acquired immunity develops through exposure to pathogens or vaccination, often with memory that provides faster responses upon re-exposure.

Innate immunity is the first line of defense and is present from birth. It includes physical barriers such as skin and mucous membranes, and cellular components such as phagocytes (neutrophils and macrophages), dendritic cells, and natural killer cells. The innate system also involves plasma proteins like the complement cascade and inflammatory mediators that recruit immune cells to sites of infection.

Adaptive immunity provides targeted and long-lasting protection. It relies on lymphocytes, notably B cells that produce antibodies and T cells that help orchestrate responses (CD4+ T helper cells) or kill infected cells (CD8+ cytotoxic T cells). Antibodies can neutralize pathogens or mark them for destruction. The adaptive system develops specificity through clonal selection and forms immunological memory, enabling rapid and robust responses to future encounters with the same antigen.

Immunological dysfunction can lead to immunodeficiency, autoimmunity, or hypersensitivity reactions. Vaccines harness adaptive immunity to prevent disease by stimulating memory responses. Aging and chronic disease can alter immune function, influencing susceptibility to infections and outcomes of immune challenges.