Which of the following cell does not have cytotoxic activity ?
**Core Concept**
The cytotoxic activity of cells is a critical component of immune response, particularly in the context of cancer and viral infections. Cytotoxic cells, such as natural killer (NK) cells and cytotoxic T lymphocytes (CTLs), are capable of recognizing and killing infected cells or tumor cells. This process involves the release of cytotoxic granules and the expression of death receptors on the target cell surface.
**Why the Correct Answer is Right**
The correct answer is related to the cell type that does not possess cytotoxic activity. Cytotoxic cells, such as NK cells and CTLs, have the ability to recognize and kill target cells through the release of cytotoxic granules and the expression of death receptors. On the other hand, helper T cells (Th cells) play a crucial role in the immune response by assisting in the activation of cytotoxic cells and the production of antibodies. They do not possess cytotoxic activity themselves.
**Why Each Wrong Option is Incorrect**
**Option A:** Natural killer (NK) cells are a type of cytotoxic cell that plays a key role in the innate immune response. They are capable of recognizing and killing infected cells or tumor cells without prior antigen exposure.
**Option B:** Cytotoxic T lymphocytes (CTLs) are a type of cytotoxic cell that plays a key role in the adaptive immune response. They are capable of recognizing and killing infected cells or tumor cells that display viral or tumor antigens on their surface.
**Option C:** Helper T cells (Th cells) do not possess cytotoxic activity and instead play a crucial role in the immune response by assisting in the activation of cytotoxic cells and the production of antibodies.
**Clinical Pearl / High-Yield Fact**
Helper T cells (Th cells) are an essential component of the immune response, and their dysfunction can lead to immunodeficiency and increased susceptibility to infections. Understanding the role of Th cells in the immune response is crucial for the diagnosis and treatment of various immunological disorders.
**Correct Answer:** C. Helper T cells (Th cells)