Chapter 8 The Immune System

The immune system Two general classifications 1.Non-specific immune system 2.Specific immune system Visit the Immune System at

Cells of the immune system

The components of non-specific immunity External mechanisms –Skin –Digestive tract –Respiratory tract –Urinary tract Internal mechanisms –Phagocytic cells –NK cells –Complement proteins –Interferons Visit The Anatomy of the Immune System at www-micro.msb.le.ac.uk/MBchB/2b.htmlwww-micro.msb.le.ac.uk/MBchB/2b.html

Phagocytosis Process by which unwanted particles are engulfed and destroyed by digestive enzymes Two major groups of cells are involved: 1.Neutrophils 2.Mononuclear phagocytes, which include: Monocytes Macrophages Tissue-specific phagocytes

Phagocytosis by a neutrophil or macrophage

Natural killer (NK) cells Non-T and non-B lymphocytes thought to be involved with immune surveillance against cancer Method by which NK cells destroy virally infected and tumor cells is unknown

Complement proteins System has nine protein components (C1 through C9) Exist in inactive state in blood and other fluids Destroy cells that have been marked for elimination by antibodies Activation of the system occurs when antibodies bind with antigens on the invading cells Series of events follow that results in water entering the cells and causing them to burst

Interferons Polypeptides that interfere with ability of viruses to replicate Produced by cells infected with viruses; act on neighboring cells to prevent infection Mechanics of the action are –Direct: produces cellular enzymes that prevent viral protein synthesis and destruction of viral messenger RNA –Indirect: stimulates NK and killer T cell activity and antibody production in plasma cells

The two classifications of the specific immune mechanisms 1.Humoral 2.Cell-mediated

Specific immune mechanisms Target antigen molecules Antigen molecules exhibit two characteristics 1.They stimulate antibody production 2.They combine with the specific antibody

The four components of humoral immunity 1.B cells 2.Plasma cells 3.Antibodies 4.Memory B cells

The components of cell-mediated immunity T cells, which give rise to: –Killer T cells –Helper T cells –Suppressor T cells –Memory T cells

B Cells –Respond to antigens presented by macrophages –After exposure, divide into Plasma cells—secrete antibodies specific to the antigen Memory B cells—remember a previous invader and eliminate them

Role of B cells in humoral immunity

Antibodies Glycoproteins produced and secreted by plasma cells Antibody itself does not directly destroy cells but activates non- specific immune mechanisms For more information, visit Antibody Production at

The T cells Killer T cells –Must be near or in contact with the cell targeted for destruction –Produce lymphotoxins –Release interferons and substances that enhance phagocytosis Helper T cells –Stimulate cytotoxic action of killer T cells –Increase antibody production by plasma cells

The T cells (cont.) Suppressor T cells –Regulate action of killer T cells and development of B cells into plasma cells –Keep immune defense from exceeding limits necessary to destroy invading organism Memory T cells –Recognize an antigen from previous exposure

Role of T cells in cellular immunity

Exercise alters several components of the immune function, including Exercise results in leukocytosis Exercise results in lymphocytosis Exercise may increase interferon levels, but the significance is unknown

HIV positive individuals and exercise Exercise does not exacerbate the progression of HIV and may slow it. Exercise can help HIV-infected individuals maintain health. Moderate aerobic exercise can increase helper T cell and NK cell counts. Resistance training can help to maintain or increase muscle mass and so diminish the weight loss characteristic of stages 2 and 3 of HIV infection. For more information, visit Comprehensive AIDS and HIV Information

How to minimize the risk of becoming ill 1.Allow sufficient time between training sessions for recovery. 2.Avoid extremely long training sessions 3.Use periodization of training 4.Avoid training monotony by ensuring variation in training load 5.When increasing the training load, do so on hard days. Don’t eliminate recovery days 6.When recovering from overtraining or illness, begin with light training and increase gradually. 7.Monitor and record mood, feelings of fatigue, and muscle soreness; decrease the training load if the session seems harder than usual.

How to minimize the risk of illness (cont.) 8.Keep other stresses to a minimum. 9.Get regular and adequate sleep 10.Get more rest after travel across time zones 11.Pay attention to diet and make sure it is well- balanced 12.Ensure adequate total dietary intake 13.Consider drinking carbohydrate sports drinks before, during and after prolonged workouts 14.Consider vaccination.

Guidelines for training and competition during an infection –Exercise tolerance may be reduced during infection –Exercising with an infection may increase the duration of the illness –Iron supplements should be avoided to limit bacterial infection –Training should be stopped if fever or systemic symptoms are present –Training should be resumed gradually –Team members with infection should be isolated as much as possible from the rest of the team