The organs, cells, and molecules responsible for the recognition and disposal of foreign (“non-self”) material which enters the body.
A precisely ordered system of cells, hormones, and chemicals that regulate susceptibility to, severity of, and recovery from infection and illness.
The complex system of cells and proteins that the body uses to protect itself from harmful microorganisms, such as viruses, bacteria, and fungi.
A complex system of interlocking substances and tissues that protects the body from disease.
The body’s ability to develop antibodies that resist disease-producing agents. The system of biochemical and cellular elements that protect the body from invading pathogens and foreign material.
A complex network of cells and cell products, which protects the body from disease. It includes the thymus, spleen, lymph nodes, white blood cells and antibodies.
Body’s defence mechanisms against infection and disease.
Immune system refers to the functional components of the body that help to fight off infections.
A complex network of specialized cells and organs that work to defend the body against attack from what are perceived as “foreign” invaders. Often these invaders, including bacteria, viruses, fungi, and parasites, are indeed foreign and dangerous, and the immune system routinely saves the body from threatening and potentially lethal attack.
Complex interactions that protect the body from pathogenic organisms and other foreign invaders (e.g., transplanted tissue), including the humoral response, chiefly involving B cells and the production of antibodies, and the cell-mediated response, chiefly involving T cells and the activation of specific leukocytes. The organs involved include the bone marrow, the thymus, and lymphoid tissue.
The complex set of mechanisms by which the body prevents or fights infection by disease-causing microorganisms such as bacteria, viruses, and fungi. The immune system also fights abnormal cells such as cancer cells. The immune system must first identify organisms or cells as harmful or abnormal, and then fight them. Some of these defenses are innate, while others are acquired as the body encounters specific organisms and responds to them.
The lymphatic tissues, organs, and physiological processes that identify an antigen as abnormal or foreign and prevent it from harming the body. The skin, mucosa, normal flora of the gastrointestinal tract and skin, and chemicals contained in tears, sebaceous glands, gastric acid, and pancreatic enzymes protect the body from pathogen invasion. The bone marrow produces white blood cells (WBCs), the primary internal defense. Lymphoid tissues, including the thymus gland, spleen, and lymph nodes, influence the growth, maturation, and activation of WBCs; lymphoid tissue in the gastrointestinal and respiratory tracts and mucous membranes contain WBCs for site-specific protection. Finally, physiologically active protein mediators, called cytokines, help regulate the growth and function of immunologically active cells.
The complex group of organs and cells that normally protects the body from infections or disease.
A complex network of glands, tissues, circulating cells, and processes that protect the body by identifying abnormal or foreign substances and neutralizing them.
The internal system that protects the body from disease by recognizing and destroying pathogens.
The body’s system of organs, tissues, and cells designed to protect itself against infections and harmful substances.
The inherent safeguards of the body that protect against diseases and infections.
The immune system is a complex network of cells and proteins that safeguards the body against harmful microorganisms like bacteria, viruses, and fungi. Additionally, it plays a crucial role in cancer control and is responsible for various phenomena such as allergies, hypersensitivity, and rejection following transplant surgeries.
The term “natural (or innate) immunity” refers to the inherent protection that every individual is born with, including the skin and mucous membranes lining the mouth, nose, throat, intestines, and vagina. It also involves antibodies or immunoglobulins, protective proteins passed from the mother to the child through the placenta. When microorganisms breach these defenses, they come across white blood cells called phagocytes, which can engulf and destroy them, along with other types of white cells, such as cytotoxic cells that have the ability to kill infected cells.
Microorganisms can also come into contact with naturally produced substances within the body, like interferon, or a group of blood proteins known as the complement system. These substances work together to eliminate the invading organisms and provide additional protection to the body.
The second component of the immune system, referred to as “acquired (or adaptive) immunity,” becomes active when the body encounters certain organisms that surpass the innate defenses. The acquired immune system responds specifically to each type of invading organism and retains a memory of the invader. This memory allows the immune system to mount an instant defense in case of any future invasion by the same organism.
The acquired immune system initiates its response by identifying a portion of the invading organism or tumor cell known as an antigen (a foreign protein to the body). Subsequently, one of two types of responses, either humoral or cellular, is launched against the detected antigen.
Humoral immunity plays a crucial role in protecting the body against bacterial infections. After a sophisticated recognition process, specific B-lymphocytes undergo multiplication and generate a large quantity of antibodies. These antibodies bind to the antigens present on the invading bacteria, marking them for destruction. Subsequently, phagocytes engulf and eliminate the bacterium. Moreover, the interaction between antibodies and antigens can trigger the complement system, boosting the efficiency of phagocytes in combating the infection.
Cellular immunity holds significant importance in protecting the body against viruses, certain parasites that reside within cells, and potentially cancer cells. This type of immunity relies on two kinds of T-lymphocytes: helper cells, responsible for recognizing antigens, and killer cells (the second type of T-lymphocyte), which are activated by helper cells and serve to eliminate invaded cells.