Question

_____________ are killed by cytotoxic T cells. a. Extracellular virus particles in blood b. Virus-infected body cells c. Bacterial cells in tissue fluiddd d. Pollen grains in nasal mucus

Short answer

Virus-infected body cells are killed by cytotoxic T cells.

Step-by-step solution

Understand the Role of Cytotoxic T Cells

Cytotoxic T cells are a subtype of T cells that play a crucial role in the immune system. They are primarily responsible for killing infected cells in the body, particularly those infected by viruses, as well as cancerous cells.

Analyze Each Option

- **Option a:** Extracellular virus particles in blood - These are not targeted by cytotoxic T cells as they are outside of body cells. - **Option b:** Virus-infected body cells - Cytotoxic T cells recognize and destroy these cells. - **Option c:** Bacterial cells in tissue fluid - These are generally targeted by other immune cells such as neutrophils and macrophages. - **Option d:** Pollen grains in nasal mucus - These are not typically targeted by cytotoxic T cells; instead, they are involved in allergic reactions.

Identify the Correct Answer

Based on the analysis, cytotoxic T cells target and kill cell types that are infected with viruses, which leaves correct option as **b, virus-infected body cells**.

Key concepts

Immune System

The immune system is like a guardian of our body, protecting us from harmful invaders. It comprises a network of cells, tissues, and organs working together to defend against pathogens.
These invaders can be bacteria, viruses, parasites, or fungi. The immune system has two main branches: the innate immune system and the adaptive immune system.

The **innate immune system** is the body's first line of defense. It acts quickly to stop the spread of infections using various barriers and cell types like skin, mucus, and macrophages.
The **adaptive immune system**, on the other hand, is more sophisticated. It takes longer to respond but targets specific microbes with precision. Cytotoxic T cells are an essential component of this system.
This part of the immune system can "remember" pathogens, offering long-lasting protection by responding more effectively to previously encountered threats.

Virus-Infected Cells

Virus-infected cells present a unique challenge to the immune system. Viruses can hijack a host's cellular machinery, replicating themselves inside.
This makes it difficult for immune cells to detect and destroy them since the virus hides within the body's own cells.

Cytotoxic T cells are the immune system's specialized "hitmen" that deal with this problem. They have the ability to recognize and kill these compromised cells.
When a virus infects a cell, it often leaves traces, such as viral proteins, displayed on the cell's surface. Cytotoxic T cells recognize these markers and then bind to the infected cell.
Once bound, they release substances that poke holes in the infected cell's membrane to eliminate the virus's hiding place.
This highly targeted approach is crucial for stopping viral infections in their tracks. It helps prevent viruses from spreading to nearby healthy cells.

Adaptive Immunity

Adaptive immunity is a targeted defense system that evolves during our lifetime, tailoring its response based on exposure to specific pathogens.
The two main types of cells involved are B cells and T cells, each playing distinct roles in combatting infections.

B cells are specialized in producing antibodies. These antibodies circulate in the blood and bind to antigens, like viruses, neutralizing them and marking them for destruction.
T cells, including cytotoxic T cells and helper T cells, are the other main players in adaptive immunity. Helper T cells aid in recruiting and activating other immune cells.
Meanwhile, cytotoxic T cells directly attack and destroy virus-infected cells by recognizing viral antigens presented on their surfaces.
Adaptive immunity is not only specific but also has memory. Once it encounters a pathogen, it "remembers" it, leading to a swifter and more robust response upon re-exposure.

• This memory capability is the principle behind vaccines which train the immune system against specific viruses without causing the disease.