Body Defenses

1. Body Defenses

2. Non-Specific Body Defenses Surface Membrane Barriers Cells and Chemicals Inflammatory Response Other Non-Specific Defenses

3. Surface Membrane Barriers Physical First line of defense The purpose is to protect the body by preventing entry and spread of microorganisms Pathogens? any harmful or disease-causing microorganisms or particles Skin Keratinized epidermis is a strong physical barrier Acidic pH of skin secretions

4. Surface Membrane/Cells and Chemicals Mucous membranes Line all body cavities open to the exterior Digestive Respiratory Urinary Reproductive Provide both physical and chemical protection Cells and Chemicals Second line of defense; attacks anything that made it by the surface membrane barriers

5. Cells and Chemicals Phagocytes Macrophages and neutrophils that act to engulf foreign particles and enclose them in vacuoles. Digestive enzymes in these vacuoles break down particles. Natural killer cells Act as the blood and lymph “police” Unique cells that can lyse and kill cancer cells and virus infected cells They are not specific to any one cell, but can act on any target by recognizing non-self cell markers. They attack cells and release toxic chemicals that target the cell’s membrane and nucleus.

6. Inflammatory Response Inflammatory Response Cardinal Signs Redness Heat Swelling Pain Steps Chemical alarm Injured cells release inflammatory chemicals (histamine and kinins)

7. Inflammatory Response (Con’t) Cause blood vessels to dilate and capillaries to become leaky Activate pain receptors Attract phagocytes to the injured area Increased blood flow to area as a result of vasodilation The area swells (local edema) due to leaking of plasma from blood vessels Accomplishments

8. Inflammatory Response (Con’t) Prevents the spread of damaging agents to nearby tissues Disposes of cell debris and pathogens Sets the stage for repair

9. Figure: 12.2

10. Other Non-Specific Defenses Other Complement Refers to a group of 20 plasma proteins that circulate in the blood in the inactive state Compliment fixation? when complement becomes attached, or fixed to foreign cells. Causes lesions in foreign cells’ membranes Amplifies inflammatory response

11. Other Non-Specific Interferon Chemical secreted by virus-infected cells that acts to protect nearby cells from viral infection Act by binding to cell membrane receptors Fever Abnormally high body temperature Systemic response to invasion by microorganisms White blood cells and macrophages that have been exposed to pathogens can secrete chemicals called pyrogens that act to raise body temperature Fever helps to increase cell metabolism and make it difficult for pathogens to reproduce

12. Specific Body Defenses Immune Response Antigens Cells of the Immune System Humoral Immune Response Antibody Function Cellular Immune Response

13. Immune Response Immune response Third line of defense Immune system cells recognize foreign molecules Cells act to inactivate or destroy them Three characteristics It is antigen specific? it recognizes and acts against particular pathogens or foreign substances It is systemic It has memory? recognizes previously encountered pathogens and mounts a quicker and stronger attack

14. Immune Response (Con’t) Two separate but overlapping arms Humoral immunity? B cells make antibodies against specific antigens Cellular immunity? T cells directly attack foreign invaders

15. Antigens Antigens Antigens vs. pathogens An antigen is any substance capable of exciting an immune system response An immune system response activates the immune system cells (B and T lymphocytes) A pathogen is any potentially harmful foreign invader. A pathogen can be an antigen, but does not have to be.

16. Antigens (Con’t) Non-self antigens Any organic substance that is recognized by the immune system cells as not being part of the body are considered non-self antigens. Most are large molecules such as all foreign proteins, nucleic acids, many carbohydrates and some lipids. Self-antigens Your own cells also contain surface markers These are mostly protein or carbohydrate markers on the cell membranes of all of your cells.

17. Cells of the Immune System An overview of immune cells Lymphocytes White blood cells that originate in red bone marrow Some immature lymphocytes are released from the bone marrow and travel to the thymus become immunocompetent (differentiate into T cells) B cells develop immunocompetence in the bone marrow, and fully develops when an antigen binds to its surface receptors

18. Cells (Con’t) Macrophages Cells that arise from monocytes formed in the bone marrow They act to engulf antigens and then present the non-self marker on its own cell membrane- like an antigen presenter These cells are then recognized by the T cells There is continual communication between the macrophages and lymphocytes

19. Humoral Immune Response Humoral Immunity Steps of humoral immune response Immature B cells are activated by an antigen binding to its surface receptors. The binding event ‘sensitizes’ the lymphocyte to go into rapid division or clonal selection. Helper T cells manage this event by sending chemical messages to the B cells. All clones have the same antigen receptor as the original. Most B cell clones then divide to become plasma cells. Plasma cells release antibodies at a rate of 2000/sec

20. Humoral Response (Con’t) Antibodies travel through the blood and bind to receptors on the specific antigen. Antibody action disrupts the antigen function. This continues for about 4-5 at the onset of the immune response, and then the plasma cells start to die out. B cells that do not become plasma cells remain as memory cells in the blood for future invasions of this specific antigen.

21. Antibody Function Antibody Function Compliment Fixation Main way for antibodies to act against cellular antigens such as bacteria and or mismatched RBC. Complement binds with antibodies attached to cellular targets. This causes cell lysis. Neutralization Occurs when antibodies bind to specific sites on bacteria cells that secrete toxins. Antibodies bind to areas where chemicals are secreted thereby blocking the action of the antigen

22. Antibody Function (Con’t) Agglutination Occurs when antibodies bind to more than one antigen. Multiple antigens in one antibody causes clumping of the foreign cells, or agglutination. Precipitation Occurs when the cross-linking process of agglutination involves soluble antigens. The clumping causes the antigen-antibody complex to precipitate out of solution.

23. Figure: 12.8

24. Cellular Immunity Cellular Immune Response Steps Helper T cells are activated to form clones by having the antigen “presented” to them by a macrophage. Helper T cells must recognize both the self and non-self antigens to be activated and this leads to cloning of the T cells. The activated Helper T cells secrete lymphokines which stimulate the proliferation of and activity of other helper T cells and activates Killer T cells and B cells.

25. Cellular Immunity (Con’t) Killer T cells directly kill virus-infected, cancer, or foreign graft cells by binding to the cells and then secreting a toxin (perforin) which destroys their cell membrane. Some of the T cells hang around after the infection to act as memory cells.

26. Figure: 12.9