Imunijärjestelmien

Imunijärjestelmien, or immune systems, are complex biological defense mechanisms that protect organisms from disease. They are composed of a network of cells, tissues, and organs that work together to identify and neutralize pathogens such as bacteria, viruses, fungi, and parasites. The immune system can be broadly divided into two main branches: the innate immune system and the adaptive immune system.

The innate immune system provides a rapid, non-specific defense that is present from birth. It includes physical barriers like skin and mucous membranes, as well as cellular components such as phagocytes (e.g., macrophages, neutrophils) that engulf and destroy foreign invaders, and natural killer cells that kill infected cells. Inflammation is also a key part of the innate response, characterized by redness, swelling, heat, and pain, which helps to recruit immune cells to the site of infection.

The adaptive immune system, on the other hand, is slower to develop but provides a highly specific and long-lasting defense. It is characterized by its ability to "remember" specific pathogens, allowing for a faster and more effective response upon subsequent encounters. Key players in the adaptive immune system are lymphocytes, specifically B cells and T cells. B cells produce antibodies, which are proteins that bind to specific antigens on pathogens, marking them for destruction. T cells have various functions, including helping B cells produce antibodies (helper T cells) and directly killing infected cells (cytotoxic T cells). The adaptive immune system is the basis for vaccination.