Definition of the Immune System The human immune system is a collective network of tissues, glands, and organs that work in a coordinated effort with each other to guard our bodies from foreign antigens such as viruses, bacteria, and infection causing microorganisms. For the immune system to work properly, two things must happen: first, the body must recognize that it has been invaded, either by pathogens or toxins or by some other threat. Second, the immune response must be activated quickly, before the invaders destroy many body tissue cells. For the immune system to respond effectively, several conditions must be in order, including the proper interaction of non-specific and specific defenses. The nonspecific defenses on the skin do not identify the antigen (a substance able to manipulate an immune response or reaction) that is attacking or potentially attacking the body; instead, these defenses simply react to the presence of what it identifies as something foreign. Often, the nonspecific defenses effectively destroy microorganisms, but if these defenses prove to be ineffective and the microorganisms manage to infect tissues, the specific defenses go into action. The specific defenses function by locating the antigen in question and mounting a response that targets it for destruction.
Organs of the Immune System The organs of our immune system are located all throughout our bodies. The main organs of the immune system are bone marrow, the thymus, the tonsils, the spleen, and the lymph nodes. Bone marrow is the soft tissue that is found inside of most of our bones. Every cell of the human immune system originate from stem cells in the bone marrow. The bone marrow then goes through a process called hematopoiesis, which produces B-lymphocytes (B-cell), immature thymocytes, red blood cells, white blood cells, and platelets. Hematopoiesis is the process wherein hematopoietic stem cells (HSC) differentiate into either lymphoid or myeloid