Quiz Over Chapter 17 Microbiology

Explanation
Cytokines are chemicals that allow cells of the immune system to communicate with each other. They are secreted by immune cells and act as signaling molecules, coordinating the response of the immune system to infections or other challenges. Cytokines can stimulate or suppress the activity of immune cells, regulate inflammation, and promote the recruitment of immune cells to sites of infection or injury. Overall, cytokines play a crucial role in maintaining immune system function and orchestrating the complex immune response.

Explanation
Adaptive immunity refers to the body's ability to specifically respond to a microbial infection. It is characterized by the presence of memory cells that allow for a faster and more effective response upon subsequent encounters with the same pathogen. This type of immunity is acquired throughout an individual's life, as they are exposed to different pathogens and develop immune responses against them. Adaptive immunity plays a crucial role in protecting the body against various infections and is a key component of the immune system.

Explanation
Antibodies are proteins produced by the immune system in response to the presence of antigens. They have at least two binding sites for antigens, which allows them to bind to multiple antigens simultaneously. The valence of antibodies refers to the number of binding sites they possess. This means that antibodies can bind to multiple antigens at once, enhancing their ability to neutralize or eliminate pathogens.

Explanation
T cells are a type of immune cell that play a crucial role in recognizing and responding to antigens. Antigens are foreign substances that can trigger an immune response. T cells are able to recognize antigens in association with major histocompatibility complexes (MHCs) on antigen-presenting cells (APCs). MHCs are proteins that present antigens to T cells, allowing them to identify and respond to specific antigens. Therefore, the correct answer is T cells because they are responsible for recognizing antigens in association with MHCs on APCs.

Explanation
The correct answer is "memory; secondary response." This is because in a secondary immune response, the body already has memory cells from a previous exposure to the antigen. These memory cells can quickly recognize and respond to the antigen, leading to a more rapid production of antibodies. In this case, the IgM production remains the same as in the primary response, but there is a rapid rise in IgG antibodies due to the activity of memory cells. The peak of antibody production occurs within 2-7 days.

Explanation
The correct answer refers to the different classes of T cells, which are distinguished based on their functions and the presence of specific cell surface glycoproteins called CDs (clusters of differentiations). T cells are a type of white blood cell that play a crucial role in the immune response. The classification of T cells into different classes helps to identify and understand their specific functions and roles in the immune system.

Explanation
Regulatory T cells (Tr) are a subset of T cells that play a crucial role in the immune response by suppressing the activity of other T cells. They help maintain immune tolerance and prevent excessive immune reactions that could lead to autoimmune diseases or allergies. By suppressing the activity of other T cells, regulatory T cells help regulate the immune system and prevent it from attacking the body's own tissues. Therefore, it can be inferred that regulatory T cells appear to suppress other T cells.

Explanation
Helper T cells, also known as Th cells, are classified as CD4 cells because they express CD4, which is an adhesion molecule that binds to MHC class II molecules on antigen-presenting cells (APCs). Once CD4 cells bind to APCs, they differentiate into Th1 and Th2 cells. Th1 cells secrete cytokines that stimulate other immune cells and help macrophages to degrade microbes that have invaded them. Th2 cells, on the other hand, are associated with parasitic infections and allergic reactions. Therefore, the correct answer is helper T cells (Th).

Explanation
This answer refers to the immune response that occurs during the first encounter with a pathogen. When the pathogen (antigen) enters the body, the immune system produces antibodies called IgM, which are the first line of defense. As the immune response progresses, IgG antibodies are also produced. However, during the initial encounter, the antibody increase is slow because the immune system is still learning to recognize and respond to the pathogen. This immune response is known as the primary response. The term "memory" is also mentioned, indicating that the immune system will remember the pathogen and mount a faster and stronger response upon subsequent encounters.

Explanation
The correct answer is cytotoxic T cells (Tc). Cytotoxic T cells, also known as CTLs, are a subset of T cells that have the ability to kill infected or abnormal cells. They are classified as CD8 cells because they express the CD8 protein on their surface, which allows them to bind to MHC class I molecules on target cells. When activated by helper T cells (Th cells), Tc cells become cytotoxic and release perforin, a protein that forms pores in the target cell's membrane. This allows granzymes, enzymes that induce apoptosis, to enter the target cell and cause its death.