Les lymphocytes T8 - SVT - SANTÉ 1ère spé #11 - Mathrix

Summary

In this video, the focus is on T lymphocytes, particularly cytotoxic T lymphocytes (CTLs), and their role in the immune system's adaptive response, specifically during HIV infection. The script outlines an experiment that demonstrates how activated T8 cells destroy infected cells, a process known as the 'kiss of death.' Through various experimental conditions, it is shown that CTLs can recognize and kill cells presenting viral proteins. The video further explains the stages of T cell activation, clonal selection, and their effector function in combating viral infections, especially in the context of AIDS progression.

Takeaways

• 😀 Cytotoxic T lymphocytes (T8) play a critical role in the adaptive immune response, targeting and destroying infected cells.
• 😀 The previous video on antibodies and B lymphocytes provides essential background knowledge for understanding T8 lymphocytes.
• 😀 In the primary infection phase of HIV, the viral load increases while the number of T8 lymphocytes decreases, reflecting the immune system's response to the virus.
• 😀 An experiment with infected mice shows that activated T8 lymphocytes are effective in recognizing and destroying infected cells expressing viral proteins.
• 😀 Lymphocytes can only destroy cells that express viral proteins on their surfaces, distinguishing infected cells from uninfected ones.
• 😀 Activated T8 lymphocytes can specifically target and kill infected cells, but non-activated T8 lymphocytes cannot perform this function.
• 😀 The 'kiss of death' refers to the process by which T8 lymphocytes destroy infected cells by releasing perforin and other molecules that induce cell death.
• 😀 T8 lymphocytes are activated when they recognize the antigen from the virus, undergo clonal selection, and proliferate to form an army of cytotoxic T cells.
• 😀 Once activated, T8 lymphocytes differentiate into cytotoxic T lymphocytes (CTLs) and can use perforin to puncture the infected cell membrane, causing it to burst.
• 😀 The immune response also includes the cleanup of dead cell debris by phagocytes, which helps maintain tissue health after cell destruction.

Q & A

What role do cytotoxic T lymphocytes (CTLs) play in the immune response?

Cytotoxic T lymphocytes (CTLs) are essential in the immune response as they recognize and kill cells infected by viruses. They destroy infected cells by either inducing apoptosis or through the release of perforin, which causes the infected cells to burst.

Why is it important to watch the previous videos on antibodies and B lymphocytes before this one?

The previous videos provide foundational knowledge on antibodies and B lymphocytes, which are crucial for understanding the role of T lymphocytes in the immune response. Without this knowledge, the concepts presented in this video would be difficult to grasp.

How do cytotoxic T lymphocytes recognize infected cells?

Cytotoxic T lymphocytes recognize infected cells by detecting viral proteins presented on the surface of the cells. These proteins are part of the infected cells' membrane, marking them for destruction.

What does the experiment with chromium 51 aim to demonstrate?

The experiment with chromium 51 aims to measure the destruction of infected cells by activated T lymphocytes. It tracks the release of radioactive chromium from dying cells, indicating cell death.

What is the significance of the 'kiss of death' in T lymphocyte activity?

The 'kiss of death' refers to the process by which cytotoxic T lymphocytes attach to infected cells and deliver lethal signals, leading to cell destruction. This interaction is critical for the immune system to target and eliminate infected cells.

What happens when activated T lymphocytes encounter infected cells in the experiment?

When activated T lymphocytes encounter infected cells, they release perforin, which forms pores in the infected cell's membrane. This leads to an influx of water, causing the infected cell to burst and die.

Why do activated T lymphocytes only kill infected cells and not healthy ones?

Activated T lymphocytes specifically target infected cells because they recognize viral antigens on the cell's surface. Healthy cells do not express these antigens, so they remain unaffected by the T lymphocytes.

What occurs during the 'recognition and clonal selection' phase of T lymphocyte activation?

In the 'recognition and clonal selection' phase, T lymphocytes recognize the antigen presented by an antigen-presenting cell. The T lymphocytes that are compatible with the antigen undergo activation and start proliferating to create a large number of identical cells.

How does the immune system ensure a rapid response if the same pathogen is encountered again?

The immune system ensures a rapid response by keeping a reserve of memory T lymphocytes after an infection. These memory cells are primed and ready to respond quickly if the same pathogen reappears, ensuring faster immunity.

What happens during the asymptomatic phase of AIDS?

During the asymptomatic phase of AIDS, the body does not show symptoms, but the viral load of HIV continues to rise. Although cytotoxic T lymphocytes (CTLs) initially help reduce the viral load, the number of these CTLs gradually decreases over time, making the body more vulnerable to opportunistic infections.