immunresponsen

Immunresponsen, or the immune response, is the coordinated set of cellular and molecular processes by which the immune system detects, responds to, and remembers pathogens, foreign antigens, and abnormal or damaged cells. It comprises two main branches: the innate immune response, which provides rapid, non-specific defense, and the adaptive immune response, which offers targeted, specific defense and immunological memory.

The innate response includes physical and chemical barriers such as skin and mucosal surfaces, as well as immune cells like neutrophils, macrophages, dendritic cells, and natural killer cells. These components recognize common features of pathogens through pattern recognition receptors, leading to phagocytosis, the release of inflammatory mediators, and activation of the complement system. Inflammation helps recruit additional immune cells and creates an environment hostile to invaders.

The adaptive response is driven by lymphocytes, notably T cells and B cells. Antigen-presenting cells, especially dendritic cells, display fragments of pathogens on major histocompatibility complex molecules to T cells, triggering clonal expansion and differentiation. Helper T cells coordinate responses, cytotoxic T cells destroy infected cells, and B cells produce antibodies that neutralize pathogens and mark them for attack. Humoral immunity involves antibodies, while cellular immunity involves T cell–mediated actions. The adaptive response also generates memory cells that provide faster and stronger responses upon re-exposure to the same antigen. Immune tolerance prevents reactions against self, and vaccines exploit memory to confer protection.

Regulation and resolution involve regulatory T cells and cytokine networks to limit the response and promote healing. Dysregulation can lead to immunodeficiency, autoimmunity, allergies, or excessive inflammation.