imunita

Imunita is the state or condition of being protected against disease, arising from the activity of the immune system. It can be innate, present from birth, or adaptive, developed in response to exposure to pathogens, vaccines, or other antigens. Immunity protects individuals and, in some cases, populations through reduced susceptibility and, in the case of herd protection, lower transmission.

The immune system comprises innate and adaptive components. Innate defenses include physical barriers such as skin and mucous membranes, phagocytic cells, natural killer cells, and the complement system. Adaptive immunity involves B lymphocytes that produce antibodies and T lymphocytes that help regulate responses and kill infected cells. Adaptive immunity can develop immunological memory, enabling faster and stronger responses upon re-exposure to the same pathogen.

Vaccination is a primary means of inducing adaptive immunity without causing disease, by introducing harmless forms of an antigen to train memory cells. Immunity can be acquired naturally through infection or artificially through vaccines and passive antibody transfer.

Clinical relevance varies with immune function. Immunodeficiencies, whether primary (genetic) or secondary (acquired), increase infection risk. Autoimmune diseases involve immune responses against the body's own tissues, while hypersensitivity can manifest as allergic reactions. Immunity can wane with age or be affected by medications, nutrition, stress, and infections.

Measurement of immunity includes antibody titers, cellular assays, and records of vaccination history. Maintaining robust immunity relies on vaccines, good nutrition, infection prevention, and, when appropriate, medical therapies to correct or manage immune dysfunction.