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.
