ATIVAÇÃO DE LINFÓCITOS B (ENSINO SUPERIOR) - IMUNOLOGIA

Summary

In this video, Cleverson del Vec explains the activation of B lymphocytes in immunology. He details two complementary ways B cells can be activated: directly by an antigen bindingTranscript Summary Request to the BCR receptor or with the help of T lymphocytes. The process occurs in the lymph nodes, where B and T cells meet and cooperate. The B cell processes the antigen and presents it to the T cell, which releases interleukin-21 to further activate the B cell. The B cell proliferates, differentiates into memory cells and plasma cells that secrete antibodies to fight invaders. The video concludes with a recap of this critical immune response process.

Takeaways

• 😀 The video explains the process of B lymphocyte (B cell) activation in immunology.
• 😀 B cell activation can occur in two complementary ways: through direct antigen binding or with the help of T lymphocytes (T cells).
• 😀 The first form of activation is when an antigen binds directly to the B cell's receptor (BCR).
• 😀 The second form of activation involves T cells assisting B cells after the T cell binds to the antigen presented by the B cell.
• 😀 The primary location of B cell activation is in the lymph nodes, where B and T cells are strategically located in different regions.
• 😀 B cells are found in the follicular region of the cortex, while T cells are located in the para-cortical area near the medulla.
• 😀 When an antigen enters the lymph node, it binds to the B cell receptor (BCR), and the B cell then processes and presents the antigen with MHC molecules.
• 😀 The processed antigen can then move to the para-cortical region, where T cells become activated and move toward the B cells.
• 😀 When B cells and T cells meet in the para-cortical region, T cells release interleukins (e.g., IL-21) to further stimulate B cell activation.
• 😀 Activated B cells proliferate in the dark zone of the germinal center, where they interact with dendritic cells to test antigen affinity and select those B cells that have a strong affinity for the antigen.
• 😀 B cells that demonstrate high affinity for the antigen differentiate into plasma cells that secrete antibodies or memory B cells that provide long-term immunity.

Q & A

What are the two primary ways B lymphocytes are activated?

B lymphocytes can be activated in two complementary ways: first, by direct binding of an antigen to the B cell receptor (BCR), and second, by the help of activated T lymphocytes that interact with the B cells.

What role do T lymphocytes play in B lymphocyte activation?

T lymphocytes assist in the activation of B lymphocytes by migrating toward them after both the antigen has activated the B cell and the T cell. They help fully activate the B cells through direct interaction.

Where do B and T lymphocytes interact in the lymph node?

B lymphocytes are located in the follicular region of the cortex of the lymph node, while T lymphocytes are found in the paracortical region. The two types of cells meet in this transitional zone to facilitate B cell activation.

How does the antigen presented by the B cell affect the T cell?

When a B cell presents an antigen using the MHC Class II molecule, it binds to the T cell receptor (TCR) on T lymphocytes. This interaction activates the T cell, which then releases interleukins, such as IL-21, to further stimulate B cell activation.

What is the significance of the interleukin IL-21 in B lymphocyte activation?

Interleukin IL-21, released by activated T lymphocytes, enhances the activation of B cells, ensuring they proliferate and fully respond to the antigen.

What happens to B lymphocytes after they are activated?

After activation, B lymphocytes proliferate in the germinal center of the lymph node. They then undergo selection, where those with high affinity for the antigen are kept, while those with low affinity are discarded.

What is the role of follicular dendritic cells in the activation of B cells?

Follicular dendritic cells display antigens to B cells in the germinal center. The B cells test their receptor affinity for these antigens, which helps select the most effective B cells for memory or antibody secretion.

What is the difference between memory B cells and plasma cells?

Memory B cells retain the ability to respond quickly to future exposures to the same antigen, while plasma cells are specialized B cells that secrete large quantities of antibodies to fight infections.

Why is the lymph node structure important for B lymphocyte activation?

The structure of the lymph node, with its distinct regions for B and T cells, allows for the necessary interactions between these cells, facilitating the activation of B lymphocytes through both antigen binding and T cell help.

What does the selection process of B cells ensure?

The selection process ensures that only B cells with a high affinity for the antigen remain, leading to the generation of effective memory B cells and plasma cells, which are crucial for long-term immunity.