Immunology

From Immunology Notes
 by Stephen Gislason MD

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 Topics from the book

Introduction to Immunity
Immune Networks
Antibodies
Immune Cells
Immune Mediators
Inflammation
Allergy Center
Food Allergy

 

Immunity is generally understood to mean protection from infectious disease. When we are ill with a viral infection such as a cold, we expect to get better, as a result of successful immune defense. Immune defense stops infection with several subdivisions, specializing in attacking one of the many micro-organisms which threaten us - bacteria, fungi, viruses, and parasites. Another role of the immune system is the defense against molecules which invade body space from the outside.

Immune defense covers all body surfaces exposed to the environment: skin, respiratory tract, gastrointestinal tract, and genitourinary tract. Immune cells are found circulating in the blood stream or patrolling in the intercellular spaces of all body tissues. Immune networks are also distributed in discrete organs of the lymphatic system which includes lymph nodes, tonsils, liver and spleen. Bone marrow is the major manufacturing area of immune cells. The thymus is the organ which develops T-lymphocytes and exerts regulatory influences on the immune system. Immunity means that immune cells remember the identity of an antigen challenge and initiate a successful defensive response. Immunizing injections contain antigens which belong to the infecting organisms. The first response to the injected antigen is the activation of antigen-specific lymphocytes who proliferate into clones of antigen-specific cells. These immune clones can later identify and attack the infecting organism. Several exposures to the vaccine (antigen) boost immune memory to an effective level of vigilance against the infecting organism.

Immune activity has a benefit and a cost. The negative side of immunity is the production of distressing symptoms, acute and chronic diseases. The terms "allergy" and "hypersensitivity" describe increased, damaging immune responses. If you read a textbook of immunology, you get the impression that immune activity only happens occasionally when an infection threatens or an obvious allergic response occurs. You may not realize that immune activity is continuous and is likely to generate symptoms in every person on a regular basis. You do learn from the immunology text that there are many hypersensitivity diseases. You do not learn that non-specific hypersensitivity states are common and produce a variety of ill-defined illnesses.

Allergy is a form of hypersensitivity.

Autoimmune diseases such as rheumatoid arthritis or multiple sclerosis are expressions of immune-mediated hypersensitivity.

Our basic theory of disease is that many patterns of illness can be explained if we recognize that substances inhaled in air and ingested as foods can trigger a variety of immune responses in any and all parts of the body.