Revisão de linfócitos B, linfócitos T CD4 e linfócitos T CD8

Summary

This video delves into the intricate workings of the immune system, focusing on B and T lymphocytes. It explains the unique role of B cells in recognizing antigens and producing antibodies once activated, with a distinction made between effector B cells and plasma cells. The script also covers T cells, specifically CD4 and CD8 types, emphasizing their function in identifying and eliminating infected or cancerous cells. Key concepts such as antigen presentation, MHC complexes, and the immune response dynamics are explored, highlighting the importance of both B and T cells in fighting pathogens and maintaining immunity.

Takeaways

• 😀 B lymphocytes have unique membrane-bound antibodies that respond to specific antigens or pathogens.
• 😀 Each B lymphocyte has a variable region on its antibody, making them capable of responding to different pathogens.
• 😀 B lymphocytes require activation from T-helper cells to fully respond to antigens and become activated.
• 😀 Once activated, B lymphocytes clone themselves and differentiate into either plasma cells or memory cells.
• 😀 Plasma cells are the true antibody-producing cells in the immune system, not B lymphocytes directly.
• 😀 The term 'plasma cells' is commonly used in immunology to refer to B lymphocytes that produce antibodies.
• 😀 T-helper cells (CD4 positive) assist in activating B lymphocytes and releasing cytokines to coordinate the immune response.
• 😀 T-cytotoxic cells (CD8 positive) target and kill infected or cancerous cells displaying antigens in MHC I complexes.
• 😀 Cytotoxic T-cells kill 'bad' cells (infected or cancerous) to prevent further damage or viral production.
• 😀 Both B and T lymphocytes generate memory cells, which allow for a faster immune response if the same pathogen is encountered again.

Q & A

What makes B lymphocytes (B cells) unique in the immune system?

B lymphocytes are unique because each one has a variable region on its membrane-bound antibodies. This variation allows different B cells to respond to different antigens and pathogens. When activated, they differentiate and clone themselves, producing a large number of antibodies specific to the antigen.

How are B cells activated to produce antibodies?

B cells are activated when a pathogen binds to the antibodies on their membrane. However, this is not sufficient alone; they also require help from activated helper T cells. The B cell processes the pathogen, presents it via MHC II complexes, and once a helper T cell recognizes the antigen, it activates the B cell.

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

Effector B cells and plasma cells are essentially the same; however, when a B cell starts producing antibodies, it is referred to as a plasma cell. The term 'plasma cell' is more commonly used in immunology to describe the B cell in its antibody-producing state.

What is the role of memory B cells?

Memory B cells are long-lived and remain in the body after an immune response. If the same pathogen is encountered again in the future, these cells allow for a faster and stronger immune response by quickly producing the specific antibodies needed.

What do effector B cells do once activated?

Once activated, effector B cells become antibody-producing machines. They produce large amounts of antibodies that bind to the antigens of pathogens, marking them for destruction by other immune cells like macrophages.

How do helper T cells assist in the activation of B cells?

Helper T cells activate B cells by recognizing antigens presented by the B cells in MHC II complexes. Once a helper T cell binds to the antigen, it releases cytokines that activate the B cell, leading to its differentiation into an effector B cell or memory B cell.

What are the differences between CD4+ and CD8+ T cells?

CD4+ T cells, or helper T cells, are involved in activating other immune cells like B cells and cytotoxic T cells. CD8+ T cells, or cytotoxic T cells, are involved in directly killing infected or cancerous cells by recognizing antigens presented by MHC I complexes.

What does MHC I and MHC II stand for, and how are they different?

MHC I (Major Histocompatibility Complex I) is present on all nucleated cells and presents antigens from within the cell, such as those from viral infections or cancer. MHC II is found on antigen-presenting cells (like dendritic cells) and presents antigens that are engulfed from outside, triggering an immune response from helper T cells.

How do cytotoxic T cells kill infected or cancerous cells?

Cytotoxic T cells recognize infected or cancerous cells by their presentation of abnormal antigens on MHC I molecules. When they bind to these cells, they release cytotoxic substances that kill the harmful cells to prevent further infection or cancer progression.

Why are cytokines important in the immune response?

Cytokines are signaling molecules that help regulate the immune response. They act as alarm signals that alert other immune cells to the presence of an infection or abnormal cells. Cytokines stimulate the proliferation of immune cells, including B and cytotoxic T cells, and help coordinate the overall immune response.