Systemic features of inflammation (fever & hypotension) are mediated by
**Core Concept**
The systemic features of inflammation, including fever and hypotension, are mediated by the release of various cytokines and mediators from immune cells. This process involves the activation of the hypothalamic-pituitary-adrenal (HPA) axis and the release of various hormones and neurotransmitters that regulate the body's response to inflammation.
**Why the Correct Answer is Right**
The correct answer is **Interleukin-1 beta (IL-1β)**. IL-1β is a potent pro-inflammatory cytokine that is released by activated macrophages and other immune cells in response to the presence of pathogens or tissue damage. IL-1β stimulates the release of other cytokines, including tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6), which in turn activate the HPA axis and lead to the release of hormones such as adrenocorticotropic hormone (ACTH) and cortisol. Cortisol, in turn, acts on the hypothalamus to induce fever and on the blood vessels to cause vasodilation and hypotension.
**Why Each Wrong Option is Incorrect**
* **Option A:** While TNF-α is a pro-inflammatory cytokine that is involved in the systemic features of inflammation, it is not the primary mediator of fever and hypotension.
* **Option B:** IL-6 is a pro-inflammatory cytokine that is involved in the systemic features of inflammation, but it is not the primary mediator of fever and hypotension.
* **Option D:** Histamine is a mediator of inflammation that is involved in vasodilation and increased vascular permeability, but it is not the primary mediator of fever and hypotension.
**Clinical Pearl / High-Yield Fact**
IL-1β is a key mediator of the systemic features of inflammation, and its release is often used as a marker of inflammation in clinical settings. It is also involved in the pathogenesis of various inflammatory diseases, including rheumatoid arthritis and sepsis.
**Correct Answer:** C.