**Core Concept**
Cell-mediated lysis of tumor cells is a process where immune cells recognize and destroy cancer cells. This process involves the activation of various immune cells, including T lymphocytes and natural killer (NK) cells, which play a crucial role in eliminating tumor cells.

**Why the Correct Answer is Right**
The correct answer involves the activation of T lymphocytes, specifically cytotoxic T cells (CTLs), which recognize and bind to tumor cells via their T-cell receptors (TCRs). This interaction triggers a cascade of events, including the release of cytotoxins, such as perforin and granzymes, which create pores in the tumor cell membrane and induce cell lysis. Additionally, CTLs can also activate apoptosis through the Fas/FasL pathway.

**Why Each Wrong Option is Incorrect**
**Option A:** While T regulatory cells (Tregs) play a role in immune suppression, they are not primarily involved in cell-mediated lysis of tumor cells.
**Option B:** Dendritic cells are antigen-presenting cells that play a crucial role in activating T cells, but they are not directly involved in cell-mediated lysis.
**Option C:** Macrophages can contribute to tumor cell destruction through phagocytosis and production of reactive oxygen species, but they are not the primary mediators of cell-mediated lysis.

**Clinical Pearl / High-Yield Fact**
When considering cell-mediated lysis, remember that the activation of CTLs is a key event in the elimination of tumor cells. This process is often impaired in patients with cancer, leading to tumor progression.

**Correct Answer:** C.