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Transcript
The Human Immune System What defenses do our bodies have against disease? Immune System Functions The Immune System helps maintain homeostatic balance by fighting pathogens and eliminating diseased cells, recycling dead cells, cell debris, and nutrients. http://www.unitedstreaming.com/index.cfm?media_file_id=1000667 Body Defenses Against Disease First line of defense Physical: cilia in respiratory tract, skin Chemical: secretions such as mucus, tears, and sweat contain lysozyme and other chemicals that fight germs; stomach acid Specific and nonspecific defenses – immune system reactions Human Immune System Lymphatic system – network of vessels that collects, filters, and returns plasma that leaks from the bloodstream. Organs and cells that filter lymph and blood and destroy foreign microorganisms Immunity – Resistance to Disease Passive – comes from outside: Antibodies in breast milk baby Antibodies produced in animal human Immune cell transplant Active – immune response produced by the body: Antibodies made in response to infection Cells that kill cancer and virus-infected cells Passive Immunity – “Borrowing” antibodies from another human being Ex.: Colostrum is rich in antibodies, comes out before mother’s milk Passive Immunity – “Borrowing” antibodies from another human being Ex.: Gamma Globulin - injected antibodies Antivenom Production Ex.: antidote against snake venom Inject Horse, rabbit, or other animal with venom; animal antibodies the horse makes are an example produces antibodies against of ACTIVE ___________ immunity.venom. Milk snake to obtain venom. The The antibodies injected into a person to treat snake bite PASSIVE are ___________ immunity. Purify antivenom from horse serum. Active Immunity – body makes its own antibodies, Permanent Protection Ex.: Immune reaction after exposure to disease some symptoms Immune Cells White blood cells -- leucocytes Made in red bone marrow found in lymph, blood, and tissues Some can migrate to area of infection Fight germs specifically and nonspecifically Bone Marrow Stem Cells Lymph Cells B-Cells T-Cells Blood Cells WBC RBC Platelets Nonspecific Defenses Effective against many types of pathogens Phagocytes engulf and kill many germs (macrophages, neutrophils) Natural killer cells kill virus infected cells Interferon – chemical defense against viruses Inflammation – histamines increase blood flow, immune cells migrate to the area Macrophage Neutrophil Inflamatory Response Specific Immunity Effective against a specific pathogen Pathogens have antigens, usually proteins, that immune cells identify as foreign Body has millions of lymphocytes, special leucocytes with receptors for specific antigens Lymph nodes – pathogens are identified: If a lymphocyte is present that has a receptor for the antigen on the pathogen, an immune reaction starts The presence of the specific receptor depends on having the gene for it. Lymphocytes & Specific Immune Responses T lymphocytes – T cells, mature in the Thymus Helper T cells* – recognize antigens, initiates immune reaction Cytotoxic T cells – kill cancer and virus infected cells cell-mediated response B lymphocytes – B cells, mature in the Bone marrow Make antibodies – proteins that bind to antigens – when activated by a helper T cell antibody-mediated or humoral response * HIV infects and kills helper T cells, stopping many immune reactions from happening. Lymphocyte Production & Maturation* + T cells* + B cells* Antigen Cytokines Ex.: interleukins or CYTOTOXIC T CELL specific for antigen is activated & replicates APC (Antigen-Presenting Cell, usually a phagocyte ) digests the pathogen & presents antigens to a helper T cell Cytotoxic T and Killer cells secrete cytotoxins that Cell Mediated kill infected body cells Immune Response * Most prevalent with intracellular parasites * Why? Must destroy infected cells. Antibody (Humoral) Response * most prevalent with extracellular parasites * 1. 2. 3. Helper T cells recognize antigens from pathogens or APC; Helper T cells activate B cells that have the proper antibody shape to start making antibodies; Antibodies bind to pathogens and mark them for destruction by phagocytes or “complement” proteins found in blood. An Antibody Molecule B cells have antibodies on their surface as receptors for activation. B cells secrete antibodies that attach to the antigens on the pathogen http://www.cellsalive.com/antibo dy.htm Antigen-binding sites Opsonization Antibodies bind to the antigen on the pathogen’s surface and “tag” the germ for destruction neutrophils phagocytosing Anthrax bacilli Complement proteins bind to antibodies attached to the germ and cause cell lysis B & T Cell Activation & Replication APC Helper T More prevalent w/ extracellular pathogens Activated B Cells replicates & secrete antibodies that stick to antigen on pathogen More prevalent w/ intracellular pathogens Activated Cytotoxic T Cells replicate & secrete cytotoxins that kill infected cells Memory Cells remain after immune reaction. Vaccination or Immunization After a specific immune reaction, memory cells may be left that recognize the pathogen Vaccination/immunization takes advantage of this: A pathogen (killed or attenuated) or an antigen from it is introduced into the body An immune reaction against the antigen happens primary response Memory cells are quickly reactivated when the real pathogen infects the host in the future secondary response, faster ↓ takes 7-10 days ↓ Much faster: 1-2 days, Hours? What do you infer from the graph? We react differently to different pathogens/diseases Some reactions are better than others Consider that: 1. The ability to make specific antibodies and cell receptors is genetic. 2. We can make 10 million+ different antibodies/receptors by shuffling DNA segments in our genes. 3. Making antibodies/immune cells against our own antigens autoimmunity Disease A Disease B Allergies (noninfectious) Immune system produces antibodies to a nonpathogenic substance found in the environment Plant pollens Dust Dust mites Various foods Autoimmunity (noninfectious) Immune system makes antibodies to proteins found in the body, destroying body’s own tissues Rheumatoid arthritis Rheumatic fever Lupus Multiple Sclerosis Biotechnology Antibodies are used in many biotech applications; ex.: immunofluorescence ELISA assay (Biology Project at U. Arizona) Immunofluorescence Antibodies with fluorescent tags can be used to label different proteins in cells.