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Immagini e concetti della biologia Sylvia S. Mader Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

C6 – Lymphatic system and immunity Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

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. Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

Lymphatic vessels Lymphatic vessels transport excess interstitial fluid (lymph) to the cardiovascular system in a one-way system. Lymph contains H2O, proteins, ions, gas and molecules for the immune response called antibodies. Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

Lymphatic system Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

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. Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

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. Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

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. Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

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. Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

The spleen Similar in structure and function to the lymph node, the spleen functions as a blood filter for pathogens and debris. Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

The first defense The first defense against diseases is nonspecific and innate. It includes various ways for contrasting pathogens. Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

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. Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

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. Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

The first defense The Inflammatory response is a localized response to pathogen attack associated with redness, warmth, swelling and pain. Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

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. Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

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. Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

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. Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

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. Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

Cells of the specific immunity Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

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) Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

Antibody-mediated immunity Vaccination is the use of antigens (a vaccine) to stimulate the immune system to clone lymphocytes B and T. Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

Cell-mediated immunity The clonal selection model works for T lymphocytes too- Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

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) Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

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). Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

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. Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

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. Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

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. Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

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. Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

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. Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

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. Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

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. Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018