**Core Concept**
Actual inflammation is a complex physiological response to tissue injury, characterized by the activation of immune cells, release of chemical mediators, and increased blood flow to the affected area. This process is mediated by various cells, including neutrophils, macrophages, and lymphocytes, which play crucial roles in the defense against pathogens and the repair of damaged tissue.

**Why the Correct Answer is Right**
The characteristic features of actual inflammation include increased vascular permeability, leading to the exudation of fluid and proteins into the interstitial space, and the migration of leukocytes into the affected area. This is mediated by the release of chemical mediators, such as histamine, bradykinin, and prostaglandins, which stimulate the contraction of smooth muscle and increase blood flow to the area. The activation of complement system and the release of cytokines, such as IL-1 and TNF-alpha, also play important roles in the inflammatory response.

**Why Each Wrong Option is Incorrect**
**Option A:** Acute inflammation is often accompanied by the presence of an infectious agent, but this is not a defining characteristic of actual inflammation.
**Option B:** While increased temperature is a common symptom of inflammation, it is not a specific feature of actual inflammation.
**Option C:** Tissue repair is an important aspect of the inflammatory response, but it is not a characteristic feature of actual inflammation.

**Clinical Pearl / High-Yield Fact**
Inflammation is a complex process that involves the coordinated action of multiple cell types and chemical mediators. Understanding the mechanisms underlying inflammation is crucial for the diagnosis and treatment of various inflammatory disorders.

**Correct Answer: D.**