Which statement best describes the difference between responses of effector B cells (plasma cells) and those of cytotoxic T cells? a. B cells confer active immunity; cytotoxic T cells confer passive immunity. b. B cells respond the first time a pathogen is present; cytotoxic T cells respond subsequent times. c. B cells secrete antibodies against a pathogen; cytotoxic T cells kill pathogen-infected host cells. d. B cells carry out the cell-mediated response; cytotoxic T cells carry out the humoral response.

Verified step by step guidance

1. Understand the roles of B cells and cytotoxic T cells: B cells, also known as effector B cells or plasma cells, primarily function in the humoral immune response by producing antibodies that target specific antigens found on pathogens. Cytotoxic T cells, on the other hand, are involved in the cell-mediated immune response, where they directly kill cells that are infected with viruses or are otherwise dysfunctional.
2. Analyze the options: Option a suggests a difference in the type of immunity conferred by B cells and cytotoxic T cells, which is incorrect as both are part of active immunity. Option b is incorrect as it misrepresents the primary and secondary immune responses; both B cells and cytotoxic T cells can be involved in primary and secondary responses.
3. Focus on the correct functions: Option c correctly identifies that B cells secrete antibodies that bind to pathogens, whereas cytotoxic T cells kill pathogen-infected host cells directly. This statement accurately reflects the distinct roles each plays in the immune system.
4. Eliminate incorrect options: Option d incorrectly swaps the roles of B cells and cytotoxic T cells, stating that B cells are involved in cell-mediated responses and cytotoxic T cells in humoral responses, which is the opposite of their actual functions.
5. Select the correct answer: Based on the analysis, the correct answer is option c, as it accurately describes the functional differences between B cells and cytotoxic T cells in the immune system.

Key Concepts

B Cells and Antibody Production

B cells, or plasma cells, are a type of white blood cell that plays a crucial role in the immune response by producing antibodies. These antibodies are specific proteins that bind to antigens on pathogens, neutralizing them or marking them for destruction by other immune cells. This process is part of the humoral immune response, which is essential for targeting extracellular pathogens.

Cytotoxic T Cells and Cell-Mediated Immunity

Cytotoxic T cells, also known as CD8+ T cells, are responsible for directly killing infected host cells, particularly those infected by viruses or transformed by cancer. They recognize infected cells through specific antigens presented on major histocompatibility complex (MHC) molecules. This function is a key component of the cell-mediated immune response, which is vital for controlling intracellular pathogens.

Active vs. Passive Immunity

Active immunity occurs when the immune system is exposed to a pathogen and produces its own antibodies, leading to long-lasting protection. In contrast, passive immunity involves the transfer of antibodies from one individual to another, providing immediate but temporary protection. Understanding this distinction is important for interpreting the roles of B cells and T cells in the immune response.