**Core Concept**
Aschoff's nodules are characteristic histopathological features of rheumatic heart disease, which is a complication of acute rheumatic fever. They represent a type of granulomatous inflammation in the heart, specifically in the myocardium or endocardium.

**Why the Correct Answer is Right**
Aschoff's nodules contain a mixture of inflammatory cells, including T lymphocytes, macrophages, and plasma cells, which form a granuloma around the site of inflammation. The center of the nodule may contain a fibrinoid necrotic area, which is a result of the inflammatory response. This fibrinoid necrosis is a hallmark of Aschoff's nodules.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the content of Aschoff's nodules.
**Option B:** This option may be a distractor, but it is not a specific characteristic of Aschoff's nodules.
**Option C:** This option is incorrect because it does not accurately describe the cellular composition of Aschoff's nodules.

**Clinical Pearl / High-Yield Fact**
Aschoff's nodules can be seen as a result of the body's immune response to Group A beta-hemolytic streptococcal infection, which can lead to acute rheumatic fever and eventually rheumatic heart disease. This is a classic example of molecular mimicry, where the immune system mistakenly targets the host's own tissues due to similarities in molecular structure.

**Correct Answer: C. Plasma cells and macrophages.**