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The Human Immune System What defenses do our bodies have against disease?

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Presentation on theme: "The Human Immune System What defenses do our bodies have against disease?"— Presentation transcript:

1 The Human Immune System What defenses do our bodies have against disease?

2 Immune System Functions The Immune System helps maintain homeostatic balance by fighting pathogens and eliminating diseased cells, recycling dead cells, cell debris, and nutrients.

3 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

4 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

5 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

6 Passive Immunity – “Borrowing” antibodies from another human being Ex.: Colostrum is rich in antibodies, comes out before mother’s milk

7 Passive Immunity – “Borrowing” antibodies from another human being Ex.: Gamma Globulin - injected antibodies

8 Antivenom Production Ex.: antidote against snake venom Inject Horse, rabbit, or other animal with venom; animal produces antibodies against venom. Milk snake to obtain venom. Purify antivenom from horse serum. The antibodies the horse makes are an example of ___________ immunity. The antibodies injected into a person to treat snake bite are ___________ immunity. ACTIVE PASSIVE

9 Active Immunity – body makes its own antibodies, Permanent Protection Ex.: Immune reaction after exposure to disease  some symptoms

10 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

11 Bone Marrow Stem Cells Lymph Cells B-Cells T-Cells Blood Cells WBC RBC Platelets

12 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 Neutrophil Macrophage

13 Inflamatory Response

14 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.

15 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.

16 T cells* B cells* + + Lymphocyte Production & Maturation*

17 Cell Mediated Immune Response * Most prevalent with intracellular parasites * Antigen digests the pathogen & presents antigens to a helper T cell Cytokines Ex.: interleukins APC (Antigen-Presenting Cell, usually a phagocyte  ) Cytotoxic T and Killer cells secrete cytotoxins that kill infected body cells or CYTOTOXIC T CELL specific for antigen is activated & replicates Why? Must destroy infected cells. 

18 Antibody (Humoral) Response * most prevalent with extracellular parasites * 1. Helper T cells recognize antigens from pathogens or APC; 2. Helper T cells activate B cells that have the proper antibody shape to start making antibodies; 3. Antibodies bind to pathogens and mark them for destruction by phagocytes or “complement” proteins found in blood.

19 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 dy.htm Antigen-binding sites 

20 Opsonization Antibodies bind to the antigen on the pathogen’s surface and “tag” the germ for destruction

21 neutrophils phagocytosing Anthrax bacilli

22 Complement proteins bind to antibodies attached to the germ and cause cell lysis KA-BOOOOM!!!

23 B & T Cell Activation & Replication Helper T Activated B Cells replicates & secrete antibodies that stick to antigen on pathogen Activated Cytotoxic T Cells replicate & secrete cytotoxins that kill infected cells APC Memory Cells remain after immune reaction. More prevalent w/ extracellular pathogens More prevalent w/ intracellular pathogens

24 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

25 ↓ takes 7-10 days ↓ Much faster: 1-2 days, Hours?

26 Disease A Disease B 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

27 Allergies (noninfectious) Immune system produces antibodies to a nonpathogenic substance found in the environment  Plant pollens  Dust  Dust mites  Various foods

28 Autoimmunity (noninfectious)  Immune system makes antibodies to proteins found in the body, destroying body’s own tissues  Rheumatoid arthritis  Rheumatic fever  Lupus  Multiple Sclerosis

29 Biotechnology Antibodies are used in many biotech applications; ex.: immunofluorescence ELISA assay (Biology Project at U. Arizona)

30 Immunofluorescence Antibodies with fluorescent tags can be used to label different proteins in cells.

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