Natural killer cells which are also called NK cells are cytotoxic lymphocytes that are different from B cells (B lymphocytes) and T cells (T lymphocytes). These natural killer cells degrade the cells which are infected by intracellular pathogens or cancer cells. A T-cytotoxic cell is T lymphocyte which kills cancerous cells or cells infected with viruses.

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Chapter 26.10, Problem 1CR

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Natural killer cells which are also called NK cells are cytotoxic lymphocytes that are different from B cells (B lymphocytes) and T cells (T lymphocytes). These natural killer cells degrade the cells which are infected by intracellular pathogens or cancer cells. A T-cytotoxic cell is T lymphocyte which kills cancerous cells or cells infected with viruses.

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B cells express a complement receptor that binds to C3b cleavage products, such as iC3b and C3dg. When a B cell with an antigen receptor that specifically recognizes that pathogen also has its complement receptor stimulated because the pathogen is opsonized with these C3 fragments, B cell activation is greatly enhanced. Due to this mechanism, B cells can be activated by much lower concentrations of antigen (in this case, the pathogen) than if the antigen is devoid of complement components. This mechanism functions to: Ensure that pathogens are readily detected by the adaptive immune system before they replicate to high levels in the host Prevent B cells from being activated in response to antigens that are not pathogens Allow B cells to phagocytose the pathogen and help destroy it Induce increased rounds of B cell replication to make more pathogen-specific B cells Allow the B cell to block pathogen replication by interfering with multiple pathogen surface functions

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Neutralizing antibodies are effective at preventing infection or toxicity mediated by pathogens or their toxic products. In fact, nearly all vaccines currently in use function by eliciting neutralizing antibodies. One example is the tetanus vaccine, in which neutralizing antibodies are generated against an inactivated form of the tetanus toxin (the tetanus toxoid). The most important feature of a neutralizing antibody is having high affinity for the antigen. being efficient at activating the complement cascade. having a high degree of multivalency, such as being a pentamer or hexamer of immunoglobulin monomers. being present at a high concentration in the circulation. 0 0 0 0