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2 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Sylvia S. Mader Immagini e concetti della biologia

3 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 C6 - Lymphatic and immune system

4 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Lymphatic system Lymphatic system has homeostatic functions and comprises lymphatic vessels and organs. Lymphatic vessels transport lymph to the blood. Lymphatic organs produce and distribute lymphocytes against pathogens.

5 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Lymphatic vessels Lymphatic vessels transport excess interstitial fluid (lymph) to the cardiovascular system in a one-way system. Lymph contains H 2 O, proteins, ions, gas and molecules for the immune response called antibodies.

6 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Lymphatic system

7 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Lymphatic organs Lymphatic organs defend the body from pathogens and are: the red bone marrow, the thymus gland, the lymph nodes and the spleen. Tonsils, Peyer patches and the appendix are patches of lymphatic tissue that face pathogens and antigens.

8 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 The red bone marrow The red bone marrow is the flexible tissue where the blood cells are produced and where B-lymphocytes (B cells) mature.

9 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 The thymus gland The thymus gland of the thorax cavity educates T- lymphocytes (or T cells), which are antigen-specific cells of the immune system.

10 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 The lymph node The lymph nodes are distributed all around the organism and are garrisons of B, T and other immune cells that cleanse the lymph of pathogens.

11 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 The spleen Similar in structure and function to the lymph node, the spleen functions as a blood filter for pathogens and debris.

12 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 The first defense The first defense against diseases is nonspecific and innate. It includes various ways for contrasting pathogens.

13 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 The first defense Barriers to entry include the skin, mucous membranes, resident bacteria and antimicrobial molecules. Complement protective proteins are antigen- activated plasma proteins. Interferon protective proteins (cytokines) can interfere with pathogen replication.

14 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 The first defense Phagocytes can be neutrophils, eosinophils, macrophages and dendritic cells. They engulf pathogens. Natural killer cells (NK cells) provide quick response to virus-infected and tumor cells.

15 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 The first defense The Inflammatory response is a localized response to pathogen attack associated with redness, warmth, swelling and pain.

16 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 The second defense The second line of defense against diseases is specific as it recognizes, responds to and remembers specific antigens. Exogenous antigens: external antigens that entered the body from the outside (i.e. bacteria or viruses). Endogenous antigens: or self-antigens, are generated within normal cell metabolism.

17 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 The second defense - fever Fever is beneficial as it tells us something is wrong. Fever creates an unfavorable environment for an invader. Fever may stimulate the immune system.

18 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 The second defense Active specific immunity is long-lived and develops naturally after infection. It can be activated (induced) by vaccination. Passive specific immunity is short-lived, it occurs when a person is given antibodies or when a mother transmits antibodies to her baby through breastfeeding.

19 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 The second defense Specific immunity responses depend on two types of lymphocytes, both produced in red bone marrow: lymphocytes B, mature in the red bone marrow and are responsible for antibody-mediated immunity; lymphocytes T, mature in the thymus gland and are responsible for cell-mediated immunity. Each B or T cell has an antigen receptor (BCR or TCR) that binds to a specific antigen.

20 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Cells of the specific immunity

21 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Antibody-mediated immunity The clonal selection model. BCR combines with an antigen Activated B cells undergo clonal selection Production of plasma cells (that produce antibodies) and memory cells (long term immunity)

22 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Antibody-mediated immunity Vaccination is the use of antigens (a vaccine) to stimulate the immune system to clone lymphocytes B and T.

23 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Cell-mediated immunity The clonal selection model works for T lymphocytes too-

24 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Cell-mediated immunity For TCR to recognize a pathogen, the antigen must be displayed to him by an antigen-presenting cell (APC) along with a MHC protein. (APC)

25 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Cell-mediated immunity The activated cell divides and, depending on the MHC, produces either cytotoxic T cells (if MHC class I) or helper T cells (if MHC class II).

26 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Cell-mediated immunity Cytotoxic T cells confer cell-mediated immunity and kill cancer, damaged or infected cells. Helper T cells coordinate cell-mediated immunity and antibody-mediated immunity by releasing cytokines.

27 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Monoclonal antibodies Antibodies produced by cloned B cells are all identical and monospecific. Hence they are called monoclonal antibodies and have many uses in both research and medicine. Monoclonal antibodies are used for medical diagnosis, pregnancy testing and cancer treatment.

28 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Abnormal immune responses Rejection of transplanted organs occurs because the immune system distinguishes between self and non-self, activating T cells. Organ rejection after transplantation can be controlled by immunosuppressive or xenotransplantation.

29 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Abnormal immune responses Autoimmune disorders are long term diseases in which immune system mistakenly attacks body tissue. Rheumatoid arthritis: complement proteins, T and B cells attack joints. Myasthenia gravis: antibodies attack neuromuscular junctions. Systemic lupus erythematosus: the immune system attack the nucleus of the body cells.

30 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Abnormal immune responses In coeliac disease, a food intolerance, the immune system attacks the small intestine in genetically predisposed people. Coeliac disease is caused by gluten proteins found in grains as wheat, causing inflammation that damages the villi lining in the small intestine. The only remedy is a lifelong gluten-free diet.

31 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Abnormal immune responses Allergies are hypersensitivities to certain allergens, as pollen, food, animal fur, that produce an immediate allergic response or a delayed allergic response. Anaphylactic shock is a dangerous immediate response characterized by a sudden drop in blood pressure.

32 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Cancer therapy Cytokines are cell-signaling proteins that stimulate white blood cells in immune responses. Interferons, interleukins and tumor necrosis factors (TNF) are cytokines used in cancer therapy.

33 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 AIDS A person affected by Acquired Immunodeficiency Syndrome can no longer respond the attacks of antigens. The syndrome results when immunodeficiency virus (HIV) damages and destroys the T cells.