Question Video: Describing the Actions and Functions of Cloned T Cells | Nagwa Question Video: Describing the Actions and Functions of Cloned T Cells | Nagwa

Question Video: Describing the Actions and Functions of Cloned T Cells Biology • Third Year of Secondary School

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The binding of a T-helper cell to an antigen on an antigen-presenting cell activates the T-helper cell to rapidly form clones of itself by mitosis. Which of the following is not a correct description of what these cloned T cells can do? [A] They can develop into memory cells that remain in the bodily fluid for a long time after the first infection. [B] They can stimulate B cells to divide and release their antibodies. [C] They can stimulate phagocytes to carry out phagocytosis. [D] They can activate cytotoxic T cells to kill body cells infected by pathogens. [E] They can differentiate into histamine-producing cells and help regulate the inflammatory response.

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Video Transcript

The binding of a T-helper cell to an antigen on an antigen-presenting cell activates the T-helper cell to rapidly form clones of itself by mitosis. Which of the following is not a correct description of what these cloned T cells can do? (A) They can develop into memory cells that remain in the bodily fluid for a long time after the first infection. (B) They can stimulate B cells to divide and release their antibodies. (C) They can stimulate phagocytes to carry out phagocytosis. (D) They can activate cytotoxic T cells to kill body cells infected by pathogens. Or (E) they can differentiate into histamine-producing cells and help regulate the inflammatory response.

Let’s remove the answer options for now and remind ourselves of the different roles activated T-helper cells can play.

Activated T-helper cells will have different roles depending on where they are activated and what chemical signals they receive. As their name suggests, the primary role of activated T-helper cell clones is to help activate other cells of the immune system. If the T cell receptor of a T cell clone recognizes its complementary MHC–antigen complex on a B cell, it will provide signals to activate the B cell. The activated B cell will then differentiate into a plasma cell which will release antibodies to fight the infection.

Through a similar interaction between a T cell receptor and an MHC–antigen complex, T cell clones can also activate phagocytes such as macrophages. Activated phagocytes will carry out phagocytosis where they engulf and digest extracellular pathogens. In addition, an activated T-helper cell clone can help to activate a cytotoxic T cell. It does this indirectly by interacting with a specific type of antigen-presenting cell called a dendritic cell. When the dendritic cell then interacts with the cytotoxic T cell through its MHC–antigen complex, it releases cytokines which fully activate the cytotoxic T cell.

Activated cytotoxic T cells will target infected cells for destruction. Some of the activated T-helper cell clones will differentiate into memory cells. Memory cells are long-lived cells which remain in the body for many years after the infection has been cleared. This means that if we are infected again in the future with the same pathogen, our memory cells can be activated to mount a much quicker and more powerful immune response.

We can therefore deduce that (E) is the correct answer to the question. Histamine is only produced by mast cells and basophils as part of the nonspecific inflammatory response, and not by T cells.

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