Lymphoid structures can be found throughout the body. While all lymphoid structures are capable of lymphocyte production, the red bone marrow and thymus are considered primary lymphoid organs because all WBCs, especially lymphocytes, originate in these organs. After production in the red bone marrow most lymphocytes and other immune cells go to secondary lymphoid organs, [...]
In contrast to nonspecific resistance, immunity (i-mu- ni-te), or specific resistance, is directed at specific antigens. An immune response involves the production of specific cells and substances to attack a specific antigen. Immunity has "memory," that is, if the same pathogen should reenter the body at a later date, the immune response is quicker and [...]
When an antigen is encountered for the first time, it stimulates T cells and B cells to become activated and proliferate, producing clones that attack and destroy the invading antigen. This is the primary immune response, and it also produces memory cells that are able to recognize the same antigen if it should reenter the [...]
Organ transplants are viable treatment options for persons with terminal disease of certain organs such as the heart, kidneys, and liver. Except for the surgery, the major problem encountered is that the patient's lymphoid system recognizes the transplanted organ as foreign and launches an attack against it. The problem is reduced by carefully determining compatibility [...]
Infectious Disorders Acquired immunodeficiency syndrome (AIDS) is a viral disease that is approaching epidemic proportions. It is caused by the human immunodeficiency virus (HIV), which attacks and kills helper T cells and invades macrophages, which serve as a reservoir for the virus. In time, the immune defenses of the victim are greatly reduced, and the [...]
Inherited, or genetic, diseases are caused by either chromosome abnormalities or specific alleles. The development of advanced techniques and new knowledge makes an understanding of genetic disease increasingly important. Chromosome Abnormalities Some genetic diseases are related to the presence of an additional chromosome or to the absence of a chromosome. These disorders result from errors [...]