The Immune System
Welcome to the wonderful, wonderful world of the Immune system (not that wonderful but pay attention, the evil AP people love torturing us with these questions). DO NOT get lost in the specifics, as the AP exam is focused on applications and conncecting ideas. In other words, it is not important to memorize the exact function of something such as mature cytotoxic T cell. You must have general ideas such as how the lines of defense (which we will delve into later) work together and what kind of white blood cells are in what defense.
Quick Preview of the Immune System
Now, before we journey into the amazing world of our immune system, let us
give you a short briefing. First, let us begin with what is called the first-line non-specific response. This is a pretty easy topic to understand. Just like the name suggests, this type of response is not specific to any type of stimuli: pathogen, antigen, etc. Instead, it involves the general defenses of the body (like mucus membranes, skin, hair follicles, etc.). The second line of defense is the non-specific patrolling cells and proteins. These fighters of the immune system attack pathogens but don't "remember" them. Leukocytes, phagocytes, macrophages, neutrophils, natural killer cells oh my!!!!! These includes the inflammatory response (this involves increase in body temperature, increase capillary permeability, attraction of macrophages, and more!). Finally, the third line of defense is the acquired immunity (active immunity). This includes specific defense with memory: B cells, T cells, and antibodies. We will delve into these types later on... but know for now that this type of response involves antibody proteins recognizing antigens. Oh, and cloning is involved. It gets a lot cooler than this! SO LEARN MORE...! |
All the important information you need to know! :D
The first line of defense, as stated, involves general defenses such as mucus membranes and skin. This defense is not at all specific! It does not discriminate nor does it care what type of pathogen is entering the body. It is not searching for a certain invader to "kick out" but rather any invader. This is nonspecific immunity; for example, when an invader enters through the nose, it will be trapped by the nasal hairs and mucus and the human body will then try to expel the invader by the common act of "sneezing". Other nonspecific immunity examples are the skin (acts as a barrier for invaders) and the pH of the stomach which is so acidic that it virtually destroys most pathogens. A nonspecific defense is often led by certain cells such as phagocytes which include macrophages and neutrophils which act as nonspecific defenders by looking for bacteria and clearing away any dead cells. This is also where the complement system comes into play, as a a complement is a protein that checks cells that need to be cleared and make sure they have a "visual ID" displaying their need for macrophages or neutrophils. The complement proteins then stimulate phagocytes to come and clear them away. This is called a complement system because the proteins act to help the immune system and nonspecific immunity with helping identify the bacteria and cells that need to be removed. INFLAMMATION (VERY IMPORTANT) is a nonspecific cellular response. The 5 steps to a 5 textbook is very great on using an example for inflammation "Let's say that you pick up a tiny splinter as you grab a piece of woods. Within our tissues lie cells known as mast cells. These cells contain histamine that calls in the cavalry and initiates the inflammation response. Entrance of the splinter damages these mast cells, causing them to release histamine, which migrates through the tissue toward the bloodstream. Histamine causes increased permeability and blood flow to the injured tissue. The splinter also causes release of signals that call in our nonspecific phagocytic cell friends, which come tot he site of the injury to clear away an debris or pathogens within the tissue. The redness and warmth associated with inflammation occur because of the increase in blood flow to the area that occurs in this process."
The next line of defense is specific as it involves lymphocytes (AKA white blood cells). Two types of lymphocytes are B cells and T cells. B cells can eventually become plasma cells and memory B cells, while T cells can eventually become helper T cells (activate B cells and recognize foreign antigens *an antigen is a foreign molecule that causes immune system response* on the surface of phagocytic cell which then they bind and produce more T cells which sends out signals for B cells to come in and "finish the job" and cytotoxic T cells (involved in cell mediated immunity). The primary immune response involves B cells that each have a different antigen recognition site on its surface. The B cell is looking for an invader with that specific antigen that it contains the recognition site for! So if a B cell goes past a foreign invader with an antigen, but that antigen does not match the site on the B cell, than the B cell will ignore it. But if the antigen and the recognition site match, than the B cells attaches to the antigen, activates, and than the B cells goes through mitosis and differentiation into either plasma cells (produce antibodies that function in the elimination of any cell containing the specific antigen and therefore they bind to the antigens and summon macrophages to come and finish the job and this is known as humoral immunity as antibodies are involved) or memory cells.
Memory cells are involved in the secondary immune response as memory cells contain stored instructions on how to destroy a specific pathogen therefore when a specific invader returns to the body, the memory cells who have already eliminated it before are able to easily recognize the invader and take care of it even faster using antibodies. Secondary response is much more effective than primary response!
Next is cell-mediated immunity which involves direct cellular response to invaders rather than antibody. Cytotoxic T cells are involved as the cells infected by the pathogen are forced to produce viral antigens therefore the cytotoxic T cells can recognize and wipe them out.
Yes, it is a lot, but re-read, watch the videos and you will be fine! The AP exam will not ask you everything about the immune system (the 2012-2013 exam didn't have a single question) but that was our exam and your exam will be much different! STUDY STUDY STUDY!
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Warning: If the video has a problem (the sound will play but you cannot see the video) please put the video to full screen and the problem should be fixed!
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Questions to consider while watching:
What do viruses do in order to gain widespread "control" of somatic cells? Macrophages can be compared to soldiers without an off switch. Why is this? What kind of immune response is exemplified by this statement? What is the main difference between a humoral and a cell-mediated response? B lymphocytes would produce a ________ in response to a specific malicious infective agent. |
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Questions to consider while watching:
What type of immune response is responsible for long term protection against pathogens? Major histocompatability complex proteins take "snap shots" of molecular "criminals" in order to help protect cells. What does this mean? Be more "scientific"! How do phagocytic cells do their work? Is this innate or acquired immunity? Why is necessary to kill both the cell housing the pathogen and the pathogen? |
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Questions to consider while watching:
When would apoptosis (a word meaning "cell suicide") be necessary? I.e. where would the pathogen have to be for this to occur? Antibodies are produced by which type of immune cell? What is the purpose of having a "cascading" effect when dealing with immune responses or many metabolic activities such as hormone signaling? |
Diagrams
The following is an assortment of helpful diagrams that will allow an easy understanding on the topic at hand. It is important to have a basic understanding on the types of cells that are involved within the immune system (antigens, B cells, T cells, and macrophages to name a few). In addition to this, we see the humoral response in a diagram below. Pay close attention to the steps since this may occur in some of those pesky essay questions! Please look at each of these diagrams and be sure to have a basic understanding of each. This will truly help you visually see the steps of the immune systems and its parts.
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If you are confused or have any questions on the immune system feel free to email us whenever you need it! :)
-Bryanna Wargat, Aidan Laliberte, and Enxhi Ferraj
-Bryanna Wargat, Aidan Laliberte, and Enxhi Ferraj
We hope our webpage helped you learn everything you could possibly know (or want to know) about the immune system. We wish you luck on the quiz and the AP EXAM!!! :O