Maharasayan Vati

An immune system is a collection of mechanisms within an organism that protects against infection by identifying and killing pathogens and tumor cells. It detects a wide variety of pathogens, such as viruses and parasitic worms and distinguishes them from the organism's normal cells and tissues. Disorders in the immune system can cause disease. Immunodeficiency diseases occur when the immune system is less active than normal, resulting in recurring and life-threatening infections. The cells of the adoptive immune system are special types of leukocytes, called lymphocytes. B cells and T cells are the major types of lymphocytes and are delivered from hematopoietic stem cells in the bone marrow killer T cell care a sub group of T cells that kill cells infected with verses (and other pathogens), or are otherwise damaged or dysfunctional. Helper T cells regulate both the innate and adaptive immune responses and help determine which types of immune responses the body will make to a particular pathogen. The immune system is a remarkably effective structure that incorporates specificity, inducibility and adaptation. Failures of host defense do occur, however, and fall into three broad categories : Immunodeficiencies, autoimmunity and hypersensitivities.