## **Core Concept**
T cells in lymph nodes are primarily found in areas where they can interact with antigen-presenting cells (APCs) and other immune cells to coordinate an immune response. The lymph node structure is crucial for understanding the distribution and function of T cells within it.

## **Why the Correct Answer is Right**
The correct answer, **paracortex**, is the area of the lymph node where T cells predominantly reside. This region is also known as the thymus-dependent zone because it is where T cells accumulate and interact with APCs, such as dendritic cells, to initiate immune responses. The paracortex is rich in T cells and is the site where T cell activation primarily occurs.

## **Why Each Wrong Option is Incorrect**
- **Option A: Medulla**. The medulla of the lymph node contains medullary cords and sinuses and is primarily populated by plasma cells and macrophages, not T cells.
- **Option B: Cortex (or more specifically, the follicles within the cortex)**. While the cortex does contain T cells, it is more specifically the site of B cell follicles and the germinal centers where B cells proliferate, differentiate, and mutate to produce high-affinity antibodies.
- **Option D: Subcapsular sinus**. This area is involved in the filtration of lymph and the initial capture of antigens and particulate matter by macrophages but is not where T cells primarily reside.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that T cells are crucial for cell-mediated immunity, and their primary location within lymph nodes (the paracortex) reflects their role in interacting with APCs to mount an immune response. This is a high-yield fact for understanding immunology and lymph node pathology.

## **Correct Answer:** C. Paracortex.