Chapter 21 - Section 21.5 - Study Guide - Assess Your Learning Outcomes - Page 845: 3

Certainly, I'd be happy to explain the process of clonal selection, the differentiation of memory cells and plasma cells, as well as the key differences between plasma cells and B cells. **Clonal Selection and Differentiation:** 1. **Clonal Selection:** When an immunocompetent B cell encounters a foreign antigen that binds to its B cell receptor (BCR), it undergoes clonal selection. This means that the specific B cell with a BCR complementary to the antigen is activated and begins to proliferate (divide) rapidly. 2. **Differentiation into Plasma Cells:** The activated B cell differentiates into plasma cells. Plasma cells are highly specialized antibody factories. They produce and secrete large quantities of antibodies specific to the encountered antigen. These antibodies circulate in the bloodstream and body fluids, binding to and neutralizing the antigen. 3. **Differentiation into Memory B Cells:** Alongside the formation of plasma cells, some of the activated B cells differentiate into memory B cells. Memory B cells are long-lived cells that "remember" the encountered antigen. They remain in the body and provide a rapid and robust immune response if the same antigen is encountered again in the future. This is the basis of immunological memory. **Plasma Cells vs. B Cells:** 1. **Function:** - **Plasma Cells:** Their main function is to produce and secrete antibodies. Each plasma cell produces a specific type of antibody that targets a particular antigen. - **B Cells:** B cells are responsible for recognizing antigens and differentiating into plasma cells or memory B cells. They are the initiators of the immune response. 2. **Lifespan:** - **Plasma Cells:** They have a relatively short lifespan, usually a few days to weeks. They produce antibodies for the duration of their existence. - **B Cells:** B cells can live for months to years, especially memory B cells which can survive for a very long time. 3. **Surface Receptors:** - **Plasma Cells:** They have reduced or no surface BCRs because their primary role is antibody production, not antigen recognition. - **B Cells:** B cells have surface BCRs that recognize specific antigens. These receptors are used for antigen binding and initiating the immune response. 4. **Antibody Production:** - **Plasma Cells:** They produce a large amount of antibodies that are released into the bloodstream and body fluids. - **B Cells:** B cells do not produce antibodies themselves. Instead, they present antigens to T cells and differentiate into plasma cells upon activation. 5. **Response to Antigens:** - **Plasma Cells:** They are the effector cells that directly combat infections by producing antibodies. - **B Cells:** They are the precursor cells that respond to antigens by differentiating into plasma cells or memory B cells. In summary, the process of clonal selection leads to the differentiation of activated B cells into plasma cells that produce antibodies and memory B cells that provide long-lasting immunity. The key difference between plasma cells and B cells lies in their functions, lifespans, and roles within the immune response.

Certainly, I'd be happy to explain the process of clonal selection, the differentiation of memory cells and plasma cells, as well as the key differences between plasma cells and B cells. **Clonal Selection and Differentiation:** 1. **Clonal Selection:** When an immunocompetent B cell encounters a foreign antigen that binds to its B cell receptor (BCR), it undergoes clonal selection. This means that the specific B cell with a BCR complementary to the antigen is activated and begins to proliferate (divide) rapidly. 2. **Differentiation into Plasma Cells:** The activated B cell differentiates into plasma cells. Plasma cells are highly specialized antibody factories. They produce and secrete large quantities of antibodies specific to the encountered antigen. These antibodies circulate in the bloodstream and body fluids, binding to and neutralizing the antigen. 3. **Differentiation into Memory B Cells:** Alongside the formation of plasma cells, some of the activated B cells differentiate into memory B cells. Memory B cells are long-lived cells that "remember" the encountered antigen. They remain in the body and provide a rapid and robust immune response if the same antigen is encountered again in the future. This is the basis of immunological memory. **Plasma Cells vs. B Cells:** 1. **Function:** - **Plasma Cells:** Their main function is to produce and secrete antibodies. Each plasma cell produces a specific type of antibody that targets a particular antigen. - **B Cells:** B cells are responsible for recognizing antigens and differentiating into plasma cells or memory B cells. They are the initiators of the immune response. 2. **Lifespan:** - **Plasma Cells:** They have a relatively short lifespan, usually a few days to weeks. They produce antibodies for the duration of their existence. - **B Cells:** B cells can live for months to years, especially memory B cells which can survive for a very long time. 3. **Surface Receptors:** - **Plasma Cells:** They have reduced or no surface BCRs because their primary role is antibody production, not antigen recognition. - **B Cells:** B cells have surface BCRs that recognize specific antigens. These receptors are used for antigen binding and initiating the immune response. 4. **Antibody Production:** - **Plasma Cells:** They produce a large amount of antibodies that are released into the bloodstream and body fluids. - **B Cells:** B cells do not produce antibodies themselves. Instead, they present antigens to T cells and differentiate into plasma cells upon activation. 5. **Response to Antigens:** - **Plasma Cells:** They are the effector cells that directly combat infections by producing antibodies. - **B Cells:** They are the precursor cells that respond to antigens by differentiating into plasma cells or memory B cells. In summary, the process of clonal selection leads to the differentiation of activated B cells into plasma cells that produce antibodies and memory B cells that provide long-lasting immunity. The key difference between plasma cells and B cells lies in their functions, lifespans, and roles within the immune response.