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Question Video: Recalling the Role of Cytotoxic T cells Biology

What would not be a target for a cytotoxic (killer) T cell?

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Video Transcript

What would not be a target for a cytotoxic, killer, T cell? Option (A) a cancerous body cell, option (B) an epithelial cell infected with COVID-19, option (C) a cell from a transplanted kidney, or option (D) a toxin released by a bacterium.

To answer this question, let’s review the function of a cytotoxic T cell. Cytotoxic T cells contain two proteins called CD8 and TCR on their cell surface. Together, they can recognize an infected host cell. This recognition, along with interleukin released by helper T cells, activates the cytotoxic T cell. An activated cytotoxic T cell releases a protein called perforin, which perforates the cell membrane of the infected cell, meaning the cell membrane gets holes in it. A cell with a damaged cell membrane is not viable and will die soon after the perforin has done its deed.

Let’s have another look at our question. The question is asking us, what would not be a target for a cytotoxic T cell? As the function of a cytotoxic T cell is the destruction of a recognized cell, the target of a cytotoxic T cell must be a cell. Answer options (A), (B), and (C) each describe a cell and can therefore be a target for cytotoxic T cells. A toxin is a molecule that has a toxic effect on cells but is not a cell itself. So, the answer to the question “What would not be a target for a cytotoxic T cell?” is (D), a toxin released by a bacterium.

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