Immune System Basics

1. Immune System Basics

2. How a Virus attacks the body.http://www.youtube.com/watch?v=Rpj0emEGShQ&feature=related

3. Pathogens • Any biological agent that causes illness and/or disease to its host. Also known as a germs, simple as that! Different types of pathogens include the following:

4. http://www.youtube.com/watch?v=Non4MkYQpYA&list=PL713E26869E18998B&index=3http://www.youtube.com/watch?v=Non4MkYQpYA&list=PL713E26869E18998B&index=3 Pathogens will trigger the immune system to respond.

5. 3 main defenses • External Barriers • Non-specific Internal (aka INNATE) Fever & Inflammatory response • Immune Response

6. External defense • Skin produces • Sweat which contains lysozymes • Oil – traps bacteria / fungi • Mucus membranes of digestive and respiratory tract produce • Mucus to trap foreign particles • Cilia sweep the mucus to be cleared from body

7. Non-specific internal defense • WHITE blood cells • Monocytes and Neutrophils • are able to cross capillary walls • use PHAGOCYTOSIS to engulf foreign invaders • Natural Killer cells • Respond to chemical message from Neutrophils; sensing molecular changes in cells causes the release of cytotoxic proteins into “foreign cell”.

8. Non-specific internal defense • Inflammatory Response • Histamines make capillary walls “leaky” • RBC, WBC, platelets and fluid cross capillary walls •  swelling, redness and warmth in the injured area •  PUS formation – tissue debris, microbes and WBC (dead and alive)

9. Non-specific internal defense • FEVER – triggered if pathogen is in bloodstream or infection is now systemic rather than localized. • 102 – 1030 F is beneficial high temp in fighting viral infections and triggers release of interferon. • Interferon literally interferes with viral replication.

10. Specific Internal Response • aka IMMUNE RESPONSE • Use Lymphocytes • B-Cells = humoral • T-Cells = cell mediated • Thymus, lymph nodes and spleen house these cells until called into action by interleukins and cytokines.

11. White Blood Cells

12. B Plasma Cells- when the B cell produces the antibody for a specific antigen, it begins to clone itself into B plasma cells, that produce more of that particular binding antibody. These cells release immunoglobulin, or antibodies. B plasma cells have a 5 to 7 day life-span; all its protein synthesis energy is going into the production of Antibodies, not self preservation. B Memory Cells- These are the same as B plasma cells, except they remain inactive until the secondary immune response Secondary immune response is considered anytime the body encounters a pathogen after the first time. Quicker response time. Primary response is the first time the body encounters a specific pathogen, Lag period before B cells respond. B cells

13. T cells Killer T cells - They find specifically coded infected cells, and then destroy them with cytotoxins. They may be directed by Helper T cells Helper T cells - secrete lymphokines that direct B cells into producing antibodies and also direct the Killer T cells as to which cell they get to eliminate. Memory T cells - derived from Helper T cells, have the same properties as their parent cell, and circulates until the body encounters the pathogen its parent cells were designer for. Suppressor T cells - in charge of slowing and stopping the immune response after the foreign substance is destroyed.

14. Antibodies & Antigens • Antigens= a fragment of a protein or peptide from the pathogen, taken to the surface of the infected cell and bound in an MHC (major histocompatibility complex) molecule. • The class 1 MHC complex molecule and the foreign peptide form the antigen, which can be read by the receptors on Killer T cells. Antibodiesare produced by B cells, when stimulated by lymphokines from helper T cells. The antibody attaches to the antigen, completing the signal, coding the infected cells for destruction. Antibodies are constructed of DNA fragments, making them so unique and almost innumerable. Antigen Cell Class 1 MHC molecule Pathogen

15. Antibodies– proteins created by B-cells that “lock” down foreign antigens • Antibodies are shaped to match antigen binding sites called epitopes. • Epitopesare the accessible portion of the antigen – a single bacterial surface protein can have several different epitopes.

16. B-cell receptors “Y” shaped proteins extend from cell membrane. 2 heavy chains 2 light chains that can be rearranged to match antigen.

17. T-cell receptors • 2 parallel protein chains • a - chain • b – chain These chains form the recognition site for each different antigen.

18. How antigen recognition by Lymphocytes works • MHC– major histocompatibility complex Chemical signaling proteins • Class I MHC – found on ALL cells • to tell self from non-self • Class II MHC – found on macrophages & B-cells • display antigens to Helper T-cells • APC – antigen presenting complex • Chemical signaling  displays antigen

19. Cell mediated immunity Cell mediated =T-Cell • Helper T-Cells respond to chemical signals presented by macrophage. • Helper T-Cells stimulate cytokines and interleukin which triggers production of B-cells and cytotoxic T-cells. • Helper T cells function in both Humoral & Cell Mediated immunity.

20. Cell mediated immunity Infected cell T-Cell Perforins • T-cells attack invaders directly • Perforins released by cytoxic T-Cells create pores in infected cell resulting in ion/water inflow cell lysis • Effective against intracellular parasites

21. T-cells interaction with antigen presenting cells • In both interactions the MHC receptor allows a T-cell to bind which starts defense response. • In (a) an infected body cell alerts cytotoxic cells to destroy infected cell (short term). • In (b) a macrophage displays antigen which triggers immune response (long term).

22. What is immunity? • The ability to resist a pathogen • Two forms of immunity; • ACTIVE– direct exposure that creates immune response. • PASSIVE– induced exposure through vaccination.

23. Immunity involves producing a primary immune response • Step one – virus or bacteria infects body cell • Step two – macrophage recognizes foreign antigen of pathogen and engulfs it presenting antigen to alert SPECIFIC DEFENSE SYSTEM

24. Development of primary immune response - continued • Step three – macrophage activates Helper T-cells • Helper T-cells set up the two prong attack of the immune response

25. Development of primary immune response - continued • Step four –Helper T-cells activate both plasma B-cells and Cytotoxic T-cells • Step five - B-cells form plasma cells which make antibodies to match foreign antigens of pathogen antibodies

26. Development of primary immune response - continued • Step five part 2- memory B-cells are created to always remember foreign antigen. • Step six – Antibodies made by plasma B-cells find & attach to pathogens antigens

27. Development of primary immune response - continued Step seven - Antibodies mark pathogens for destruction. Step eight - Cytotoxic T-cells locate and destroy infected cell by making a hole in the cell membrane.

28. Immune Response  2-prong attack triggered when Helper T-cells are alerted 5b. Creation of Memory B-cell

29. Immunological Memory • The reason why vaccines make sense, and we eventually build a tolerance to certain diseases… Vaccination is an introduction of a dormant or dead pathogen, which allows our body to do its primary immune response without the risk of actual sickness. It’s because after every encounter with a pathogen, both the T cells and the B cells differentiate into an inactive form of their parent cell. They remain inactive until the second immune response for that specific pathogen.

30. How do vaccines work? • Vaccine contains a dead or weakened pathogen or protein from pathogen. • Most vaccines are only effective against infections before you get them. • Vaccines can wear off overtime  booster shots revive immunity.

31. ImmunologicalMemory Heightened secondary response is due to long lived memory cells as a result of first exposure to antigen A.

32. Immune Response  2-prong attack triggered when Helper T-cells are alerted