B Cell Recognition and Elimination

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Questions and Answers

What is the main purpose of the immune system?

To produce antibodies and B cell receptors

To attack the body's own cells and proteins

To fight foreign substances like bacteria and viruses (correct)

To distinguish between self and non-self cells

What is the critical function of B cell receptors?

To produce antibodies and activate B cells

To distinguish between self and non-self cells

To bind to the body's own proteins and cells

To bind to foreign substances like bacteria and viruses (correct)

What is unique about each B cell?

Their ability to produce antibodies and activate B cells

Their unique set of B cell receptors and antibodies (correct)

Their ability to distinguish between self and non-self cells

Their ability to fight against only specific types of bacteria

How are B cell receptors and antibodies generated?

Through a random process involving DNA shuffling Signup and view all the answers

What is the main challenge in understanding the immune system's function?

How it distinguishes between self and non-self cells Signup and view all the answers

What would happen if the immune system fails to distinguish between self and non-self cells?

It would only attack the body's own cells Signup and view all the answers

What is the significance of the B cell receptor's binding to foreign substances?

It helps the immune system to eliminate the foreign substance Signup and view all the answers

Why is it important for the immune system to not attack the body's own cells?

To prevent autoimmune diseases Signup and view all the answers

What happens to B cells that recognize self-molecules in the bone marrow?

They are killed to prevent an autoimmune response. Signup and view all the answers

Why is it possible for B cells to react to the body's own proteins?

Because they are created at random Signup and view all the answers

Why doesn't a B cell die when it interacts with a bacteria it's meant to fight?

Because it's in a different environment with different rules. Signup and view all the answers

What would happen if an antibody binds to all the insulin in the blood?

Insulin would be unable to perform its function Signup and view all the answers

Why is it important to eliminate B cells that react to self?

Because they can react to the body's own proteins Signup and view all the answers

What is the purpose of the weeding out of B cells that react to self proteins in the bone marrow?

To prevent autoimmune responses. Signup and view all the answers

What happens to T cells that react to self proteins in the thymus?

They are killed to prevent an autoimmune response. Signup and view all the answers

Where do B cells get their unique antibody receptors?

In the bone marrow Signup and view all the answers

What happens to a B cell that escapes the weeding out process in the bone marrow and reacts to a self protein?

It ingests the self protein and presents it on an MHC II molecule. Signup and view all the answers

How does the body figure out which B cells react to self?

By keeping around various proteins in the bone marrow Signup and view all the answers

Why does a B cell need a T cell to activate it?

To receive additional signals to become activated. Signup and view all the answers

What happens to B cells that bind to self-proteins in the bone marrow?

They are eliminated Signup and view all the answers

Why is it equally applicable to talk about T cells in this context?

Because T cells also have a receptor generated at random Signup and view all the answers

Where does the interaction between the B cell and T cell usually take place?

In a lymph node. Signup and view all the answers

What is the second mechanism of defense against autoimmune responses?

The requirement for T cell activation of B cells. Signup and view all the answers

What is the purpose of vetting B cells in the bone marrow?

To eliminate those that react to self Signup and view all the answers

What is the result if both a B cell and a T cell that react to self proteins escape their respective weeding out processes?

An autoimmune response is guaranteed. Signup and view all the answers

What would happen if a B cell receptor binds to a self-protein in the bone marrow?

The B cell would be eliminated Signup and view all the answers

Why is it not possible to completely prevent the creation of B cells that react to self?

Because B cells are created at random Signup and view all the answers

What might happen if bacteria get into the bone marrow?

The B cells will bind to the bacterium and be killed. Signup and view all the answers

What happens to B cells when they bind to something at this stage?

They are killed. Signup and view all the answers

Why is it not a major problem if bacteria get into the bone marrow?

The bacteria will be killed or gone after some time, and B cells can be produced again. Signup and view all the answers

What happens to the B cells that react to the bacterium and are already in the lymph nodes?

They proliferate and lead the fight against the infection. Signup and view all the answers

What is autoimmune disease?

A disease where the immune system attacks itself. Signup and view all the answers

What is the result of the autoimmune disease myasthenia gravis?

The muscle fibers become weaker and the person becomes paralyzed. Signup and view all the answers

Why do antibodies against the receptor on the muscle fiber cause problems?

They stop the receptor from functioning or cause it to be destroyed. Signup and view all the answers

What is the role of the receptor on the muscle fiber?

To receive signals from the neuron and activate the muscle fiber. Signup and view all the answers

What would happen if antibodies bind to the receptor on the muscle fiber?

The muscle fiber would not be able to react to neuron signals. Signup and view all the answers

What is the name of the autoimmune disease where antibodies bind to the receptor on the muscle fiber?

Myasthenia gravis. Signup and view all the answers

Study Notes

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

The process of B cell recognition and elimination of self-molecules in the bone marrow, ensuring immune tolerance. Learn how B cells are vetted and proceed to lymph nodes to become active.