Lesson 15 - Immune System

Alright, now we have tackled the cardiovascular system, let's go to the immune system.

Please, print out the lecture notes prior to watching the videos. Answer the review questions below prior to class to [email protected] Thank you.

Class Handouts:
Immune System - full pager
Immune System - 2 per page
Immune System - 3 per page

Lecture Videos:

Preview Questions:
(printable Version)

14.1. We are constantly exposed to the environment. Many of the other life forms we encounter are friendly in nature and actually even help us live. For example, without the ‘good’ bacteria in our gut, we would perish ourselves. However, the outside world also brings danger to the body that can harm us; on a microscopic level, these are often viruses, bacteria, toxins, pollutants, and more. What part of our body creates a boundary (remember, having a boundary is a life function for cellular organisms) that doesn’t let foreign substances into the body in the first place?
14.2. Once an invader makes it into the body, we have two main means of combatting it; a non-specific one in which the body recognizes something is foreign and in need of battling it, and a specific one that learns to combat specific pathogens previously encountered. What is the trigger for the non-specific immunity?

14.3. Visualize a cut in the skin, an opening for foreign material to enter the body. The cut itself damaged capillaries and small blood vessels, which leak blood out. The body also floods the area by vasodilating (widening) the blood vessels in the area. Neutrophils (the most numerous white blood cell group) then travels to the site of injury to start cleaning up the mess as soon as possible. What body reactions are caused by the vasodilation and damaged capillaries? (hint: cardinal signs of inflammation)

14.4. A cell type that is deadly to invaders is the natural killer cell (NK). The NK’s recognize stressed out cells in the absence of other infection indicating markers. They attack their prey via ‘protein bullets’ poking holes into their cell membrane causing them to perish. What protein do they use to perforate their targets?

14.5. In order to understand specific immunity, we should first discuss the Major Histocompatibility Complex (MHC). Remember the cell’s glycocalyx? The fuzzy, sugary coat on it’s surface that helps with inter-cellular communication? (it’s discussed in the cell chapter if you need to read up on it; or simply look it up on google).The MHC is part of the clycocalyx. Normally, it combines with our own protein fragments. If a cell is infected however, it displays the antigen part of the pathogen. This triggers a ‘molecular alarm’ mobilizing the specific immunity. What happens if the body can’t recognize ‘self’ from ’non-self’?

14.6. Now, we have some of our cellular heroes (many are macrophages) eat a pathogen, digest it to render it harmless, and then display their antigen together with the MHC on it’s surface. What does that activate?

14.7. Infected macrophages produce signaling proteins that help the proper immune response by inducing fevers and such. What are those chemicals called?

14.8. When the body encounters a new pathogen, B- & T-cells learn to recognize it. This way, when the body is exposed again, it can fight the ‘bad’ stuff quickly and furiously. Besides learning about pathogens, the lymphocytes (B-&T-cells) need to learn of how to recognize ‘self’, the MHC. T-cells get schooled in the thymus gland, which sits behind the sternum. Where do B-cells learn the MHC?

14.9. Our immune system attacks a specific pathogen in a couple of ways. Some lymphocytes (T-cells) directly ‘shoot’ an unwanted invader, others (B-cells) make antibodies (specific proteins), that then cling themselves to the antigen part of the pathogen, rendering it harmless that way. This coordinated ‘double’ attack gets initiated by T-helper cells, which are activated when they bind to a MHC-antigen fragment on another cell (APC). For once, they bind to specific B-cells (that also show the MHC-antigen fragment) and activate them. What do those B-cells then do to help the immune attack on a specific ‘bad’ guy?

14.10. Activated T-killer (cyto-toxic) cells are kind of like ‘sharp shooters’. They hunt down their prey and kill it with protein bullets (called perforins). What do T-suppressor cells generally do?

14.11. B-cells (B-lymphocytes) are specific to one pathogen. Some B-cells that learned to recognize a specific invader remain from a previous encounter. We call them memory B-cells, because their surface is filled with antibodies that recognize a specific antigen again in the future. How do they help the immune reaction once activated?

14.12. Antibodies are globular proteins that can attach themselves to the antigenic part of a pathogen rendering it harmless. Can you describe some of the mechanisms antibodies use to accomplish that? 14.13. A body reacts to an invader much quicker once it learns to recognize it after an initial encounter. If we can expose the immune system to an antigen without making the body ill, potentially deadly pathogens can become less harmful. This is the brilliance of vaccines, a way to artificially stimulate a body’s own immune cells. We can also give a body immune support passively without activating it’s own immune system. How is that done, both naturally and artificially?

14.14. Immune cells are dispersed throughout our body. In places where we are exposed heavily, the body forms clusters of them within lymphoid organs. Before they migrate to those places (secondary lymphoid organs), they need to learn to recognize the body’s own self (the MHC complex). In which two places do they learn that?

14.15. In the thymus, T-cells learn to recognize self and differentiate it from non-self. Where is the thymus located? And why do you think is it most developed in newborns?

14.16. Many lymphocytes reside within lymph nodes embedded inside reticular fiber meshworks. They monitor and filter lymph, which is interstitial body fluid picked up in the periphery and brought back to the heart. More vessels feed into a lymph node then leave it. Why do you think that is useful?

14.17. The spleen is similar to lymph nodes. However, instead of filtering lymph, what does it monitor and filter?

14.18. Give two examples of lymphoid tissue found within mucous membranes.

Please email the answer back to [email protected] prior to class to receive credit.
Thank you.

Immune System Instructor Slides

No lab for this class.

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