Questions and Answers
What is the main purpose of the immune system?
What is a critical aspect of B cell receptors and antibodies?
What do antibodies bind to?
What is the significance of the B cell receptor?
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Why is it challenging for the immune system to distinguish self from non-self?
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What is unique about each B cell?
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What is the role of the B cell nucleus?
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How do B cells acquire their unique B cell receptors?
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What is the main reason why the body is in danger of creating B cell receptors and antibodies that can react to its own body?
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What would happen if a B cell receptor reacts to insulin?
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Why is it important to have a mechanism to get rid of B cells that react to self?
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Where do B cells get their unique antibody, or B cell receptor?
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What is the purpose of keeping various proteins around in the bone marrow during B cell development?
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What happens to B cells that bind to proteins in the bone marrow during development?
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Why is it equally applicable to talk about T cells in this context?
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What would happen if the body did not have a way to eliminate B cells that react to self?
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How are B cell receptors and antibodies created?
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What is the purpose of the process of eliminating B cells that react to self in the bone marrow?
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What happens to B cells that recognize self-molecules in the bone marrow?
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Why does the weeding out process of B cells that react to self-proteins not happen in the lymph node?
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What is the purpose of B cells presenting proteins on MHC II molecules?
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What happens to T cells that react to self-proteins in the thymus?
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Why can't B cells that escape the weeding out process in the bone marrow activate without T cells?
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What is the second mechanism of defense against self-reaction?
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Where does the 'cellular kiss' between B cells and T cells usually occur?
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What happens to B cells that do not react to self-proteins in the bone marrow?
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Why is it necessary to have both mechanisms of defense against self-reaction?
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What is the purpose of the weeding out process of B cells that react to self-proteins?
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What is a possible consequence if bacteria enter the bone marrow?
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Why is autoimmune disease not a significant problem in this scenario?
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What happens to the receptor on the muscle fiber in myasthenia gravis?
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What is the result of myasthenia gravis?
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What is the significance of B cells already present in the lymph nodes?
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What is the primary function of the receptor on the muscle fiber?
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What happens if the bacterium remains in the bone marrow for an extended period?
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What is the consequence of autoimmune disease?
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Why can the body still fight the infection even if the B cells in the bone marrow are killed?
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What is the significance of the example of myasthenia gravis?
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What is the main challenge of the immune system?
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How are B cell receptors and antibodies generated?
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What would happen if the immune system failed to distinguish self from non-self?
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What is unique about each B cell?
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Why is it important for the immune system to distinguish self from non-self?
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What happens to the B cell receptor once it becomes active?
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Why is the process of distinguishing self from non-self not obvious?
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What is the significance of the B cell receptor?
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What happens to B cells that react to self in the bone marrow?
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Why is it challenging to create a B cell receptor that only reacts to non-self?
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What is the purpose of keeping various proteins around in the bone marrow during B cell development?
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What would happen if a B cell receptor reacts to insulin?
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Why is it important to eliminate B cells that react to self?
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What is unique about each B cell?
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Why is it equally applicable to talk about T cells in this context?
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What happens to B cells that bind to self-proteins in the bone marrow?
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What is the significance of the process of eliminating B cells that react to self-proteins?
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What would happen if the body did not have a way to eliminate B cells that react to self-proteins?
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What happens to B cells that recognize self-molecules in the bone marrow?
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Why doesn't a B cell die when it interacts with a bacterium it's meant to fight?
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What is the purpose of a B cell presenting a protein on an MHC II molecule?
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What happens to T cells that react to self-proteins in the thymus?
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What is the second mechanism of defense against self-reaction?
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Why is it necessary to have both mechanisms of defense against self-reaction?
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Where does the 'cellular kiss' between B cells and T cells usually occur?
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What happens to a B cell that escapes the weeding out process in the bone marrow?
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Why is it important to have a mechanism to eliminate B cells that react to self?
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What is the purpose of the weeding out process of B cells that react to self-proteins?
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What happens to B cells that bind to a bacterium in the bone marrow?
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Why is autoimmune disease not a significant problem in the scenario where bacteria enter the bone marrow?
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What is the result of the autoimmune disease myasthenia gravis?
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Why are B cells already present in the lymph nodes significant?
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What happens to the receptor on the muscle fiber in myasthenia gravis?
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Why can the body still fight the infection even if the B cells in the bone marrow are killed?
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What happens if the bacterium remains in the bone marrow for an extended period?
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What is the primary function of the receptor on the muscle fiber?
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What is the consequence of autoimmune disease?
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Why is it possible for autoimmune disease to occur?
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Study Notes
The Immune System and Self
- The immune system's purpose is to fight foreign substances (bacteria, viruses, etc.) that enter the body
- The immune system must distinguish between "self" (one's own body) and "non-self" (foreign substances) to avoid attacking itself
B Cells and Antibodies
- B cells have unique receptors that bind to foreign substances (antigens)
- B cell receptors are generated randomly and are different for each B cell
- B cells can create antibodies that bind to specific antigens
- Antibodies can react to both foreign substances and self-antigens (proteins in one's own body)
Random Creation of B Cell Receptors
- The random creation of B cell receptors means that some may react to self-antigens
- This poses a risk of the immune system attacking itself
- There is no way to prevent the creation of B cells that react to self-antigens
Eliminating Self-Reactive B Cells
- In the bone marrow, B cells are vetted to remove those that react to self-antigens
- Proteins from the body are present in the bone marrow to test B cells
- B cells that bind to self-antigens are killed
- This process is not foolproof, and some self-reactive B cells may escape
T Cells and Self-Reactive Immunity
- T cells also have unique receptors that are generated randomly
- T cells can react to both foreign substances and self-antigens
- The process of eliminating self-reactive T cells occurs in the thymus
Second Mechanism of Defense
- Even if a self-reactive B cell escapes, it usually requires a T cell to activate it
- The activation process involves the B cell presenting a piece of the self-antigen on an MHC II molecule
- The T cell must recognize the self-antigen and interact with the B cell to activate it
- This second mechanism of defense provides an additional layer of protection against self-reactive immunity
Autoimmune Disease
- Despite these mechanisms, the immune system can still attack itself, leading to autoimmune disease
- Autoimmune disease occurs when the immune system mistakenly attacks the body's own tissues and organs
- One example of an autoimmune disease is myasthenia gravis, which is characterized by muscle weakness caused by antibodies against muscle receptors
The Immune System and Self vs Non-Self
- The immune system's purpose is to fight foreign substances like bacteria and viruses, but it needs to distinguish between self and non-self to avoid attacking the body itself.
- The question of how the immune system knows not to attack itself is not obvious, and the answer lies in how B cells and T cells are generated and controlled.
B Cells and Antibodies
- B cells have unique B cell receptors that bind to foreign substances, which later become antibodies that help remove them from the body.
- Each B cell has a different receptor, generated at random through DNA shuffling, which means some might react to the body's own proteins and cells.
- This random generation process puts the body at risk of creating B cells and antibodies that react to self, which could lead to autoimmune diseases.
Preventing Self-Attack
- The body has mechanisms to prevent B cells that react to self from being activated:
- In the bone marrow, where B cells mature, the body keeps a selection of its own proteins to test the B cells' receptors. If a B cell binds to one of these proteins, it is killed.
- This process weeds out B cells that react to self, ensuring that only those that react to non-self proteins and cells are activated.
- The same process occurs for T cells, which mature in the thymus and are also tested for self-reactivity.
Second Mechanism of Defense
- Even if a B cell that reacts to self escapes the bone marrow, it usually needs a T cell that also reacts to self to activate it.
- This second mechanism of defense ensures that most autoimmune reactions are prevented, as both a B cell and a T cell need to escape their respective weeding-out processes to trigger an immune response.
What Can Go Wrong
- If bacteria infect the bone marrow, B cells that react to the bacteria might be killed, making it harder for the body to fight the infection.
- Autoimmune diseases can still occur when the body's mechanisms fail, leading to the immune system attacking the body's own cells and tissues.
- An example of autoimmune disease is myasthenia gravis, where antibodies attack the receptors on muscle fibers, preventing muscle activation and leading to muscle weakness.
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Description
Learn about the immune system's role in distinguishing between self and non-self, and how B cells and antibodies fight foreign substances.