* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download immune system 2010
Survey
Document related concepts
Complement system wikipedia , lookup
DNA vaccination wikipedia , lookup
Immunocontraception wikipedia , lookup
Hygiene hypothesis wikipedia , lookup
Lymphopoiesis wikipedia , lookup
Sjögren syndrome wikipedia , lookup
Immune system wikipedia , lookup
Monoclonal antibody wikipedia , lookup
Psychoneuroimmunology wikipedia , lookup
Molecular mimicry wikipedia , lookup
Cancer immunotherapy wikipedia , lookup
Adaptive immune system wikipedia , lookup
Adoptive cell transfer wikipedia , lookup
Innate immune system wikipedia , lookup
Transcript
THE IMMUNE SYSTEM Populations & Ecosystems 2011 • Pathogens can enter the body via: • Inhalation • Wounds in the skin • Through mucous membranes (moist surfaces); trachea, urinary tract, vagina, digestive tract • Body fluids; blood transfusion, seminal fluid, saliva, breastmilk • Transplanted organs • We need protection from pathogens, or we would quickly die from infections. • “The boy in the bubble”- there is a rare genetic disease where the immune system doesn’t develop. Unless protected from pathogens, patients die within a few months. • The most famous case was David Vetter (1971-1984). • He spent his entire life in an enclosed room, until he received a bone marrow transplant from his sister. He died soon after from the effects of a virus that he received in the bone marrow from his sister. The immune system • Innate (nonspecific) immunity • Anatomic Barriers • Physiological Barriers • Phagocytic Barriers • Inflammatory Barriers • Adaptive (specific) immunity • Humoral Immunity - B cells and Antibodies • Cellular Immunity - T cells • Clonal Selection Theory Innate immunity (non-specific) • Not specific to a particular pathogen • First barriers to an invading pathogen • Controls most infections Skin • Skin • Physical barrier • 3 layers • outer layer (epidermis) made up largely of the structural protein keratin • waterproof and barrier to infection • Oil & sweat give the skin a pH of 3-5 • Lysozyme (enzyme also found in tears) destroys bacteria • Mucous membranes- respiratory, urogenital & gastrointestinal tracts (wet surfaces) • Trachea has lining (epithelial) cells • Mucous catches foreign material • Fine beating cilia move the layer of mucous up away from the lungs • Vagina and urinary tract are acidic Phagocytic barrier • Phagocytes engulf and destroy pathogens • Macrophages, neutrophils, monocytes, eosinophils Physiological barriers • Temperature • Raised body temperature inhibits some pathogens • Low pH (e.g. stomach) • Chemical mediators • lysozymes in tears, sweat and mucous digests cell walls of many bacteria Inflammatory response • Chemicals (particularly histamine) are released from injured areas • Attract white blood cells • Cause vasodilation • Increase permeability of blood vessels • Redness, swelling, heat • Pain • Complement system • Consists of special proteins circulating in the blood • When activated, the proteins make a hole in bacterial cell membranes • Fluid rushes into the bacteria & they explode! Adaptive immunity • The body responds to specific pathogens • Cell mediated immunity: phagocytic lymphocytes ‘eat’ pathogens • Humoral immunity: lymphocytes produce antibodies Lymphocytes • Found in: • Blood • 20-40% of white blood cells • Lymphatic tissues • Tonsils, lymph nodes, spleen • There are several types of lymphocytes: • B cells (B lymphocytes) - activated to become plasma cells - secrete antibodies • T cells (T lymphocytes) - TH cells - CD4+, cytokine secreting - TC cells - CD8+, cytotoxic (killer) cells Antigens • Antigens are proteins or carbohydrates which are foreign to the body • Antigens are found on the surface of bacteria, viruses, transplanted cells etc… • Anything that stimulates production of antibodies is an antigen • Antibodies are proteins with binding sites which stick to specific antigens • Ab’s surround foreign materials & inactivate them • Then the antibodyantigen complexes can be phagocytosed Antibodies: • Neutralisation • Agglutination • Opsinisation • Antibodies bind to bacteria, enhancing phagocytosis • Activate complement system T lymphocytes • T lymphocytes respond to antigens that are presented to them by macrophages • Develop into four cell types: Helper T cells- detect infection, initiate cytotoxic T cells & B cell response Cytotoxic T cells- destroy virus-infected cells & cancer cells Suppressor T cells- inhibit T & B cells to dampen response when pathogen is gone Delayed hypersensitivity T cell- causes transplant rejection & inflammation in allergic reactions B lymphocytes • B cells recognise and bind to antigens • Develop into two cell types: Plasma cells- produce antibodies specific to an antigen Memory cells- long-lived cells which recognise antigens and quickly multiply to produce plasma cells Antigens are detected by macrophages and presented to helper T cells. 2. Helper T cells recognise the antigens as foreign. a) They stimulate B cells (plasma cells) to produce antibodies. b) They also stimulate killer T cells and macrophages. 3. Afterwards, some B cells remain as memory cells. 4. If the antigen is presented to them again, they produce plasma cells. 5. The plasma cells produce antibodies very quickly. 1. HIV/AIDS • HIV infects the helper T cells (CD4+ cells) and destroys them. • This means that the immune system can’t recognise antigens and respond to them. • Patients develop secondary infections- bacterial, viral and fungal diseases (AIDS- acquired immune deficiency disease) Clonal selection theory • Lymphocytes recognise foreign antigens • But only one antigen is recognised by each lymphocyte • Once one lymphocyte is activated, it multiplies into cloned cells which all recognise the antigen (clonal expansion) • Memory cells are ready to multiply rapidly if exposed to the antigen again • Lymphocytes that recognise self-antigens are removed • Active immunity= body actively producing Ab • Passive immunity= Ab from an external source • Antibodies in breast milk • Antiserum given after exposure to snake venom • Natural immunity= due to natural exposure • Artificial immunity= due to immunisation Immunisation • The subject is exposed to an attenuated (weakened) or killed version of the bacteria or virus, or from the viral protein coat. • The body produces Ab & memory cells (primary response) • If exposed again later, memory cells detect the antigen & Ab production occurs very rapidly (secondary response) Current immunisations • Include (but not limited to): • Diphtheria • Whooping cough (pertussis) • Tetanus • Measles • Polio • Rubella • Hepatitis A & B Benefits Dangers Some diseases can be completely eradicated e.g. smallpox Immunity may only last for several years, requiring booster shots Death & long term disabilities caused by disease are decreased e.g. prevention of disabilities caused by prenatal rubella Herd immunity may cause complacence less immunisation & the disease can re-emerge Financial benefits due to less time lost due to illness Some vaccines may cause side effects Herd immunity- if >90% of the population are immune disease can’t spread between people If attenuated live vaccines are used, the possibility exists for the organisms to mutate & cause disease again Autoimmune diseases • In autoimmune diseases, the body’s immune system fails to recognise parts of the body and attacks them. • Rheumatoid arthritis • Juvenile (type I) diabetes (the immune system destroys the beta cells in the pancreas that produce insulin) • Multiple sclerosis