**Core Concept**
Borderline leprosy is a clinical subtype of leprosy that falls between the two extremes of tuberculoid and lepromatous leprosy. It is characterized by a wide range of skin lesions and nerve involvement, with a variable bacterial load.

**Why the Correct Answer is Right**
The characteristic feature of borderline leprosy is its immunological profile, which is neither strongly Th1 (tuberculoid) nor Th2 (lepromatous) dominant. The immune response in borderline leprosy is often described as "borderline" because it exhibits features of both polar forms, resulting in a mixed cellular and humoral response. This mixed response is thought to be responsible for the variable clinical manifestations seen in borderline leprosy.

**Why Each Wrong Option is Incorrect**
**Option A:**
This option is incorrect because it does not accurately describe the immunological profile of borderline leprosy.

**Option B:**
This option is incorrect because it describes a feature more commonly associated with lepromatous leprosy, which is characterized by a strong Th2 response and a high bacterial load.

**Option C:**
This option is incorrect because it describes a feature more commonly associated with tuberculoid leprosy, which is characterized by a strong Th1 response and a low bacterial load.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the clinical classification of leprosy is based on a combination of skin lesions, nerve involvement, and bacterial load, rather than a single criterion.

**Correct Answer: C.**