**Core Concept**
The initial step in lymphatic fluid resorption involves the contraction and relaxation of smooth muscle cells surrounding the lymphatic vessels, creating a pressure gradient that facilitates the movement of fluid into the lymphatic capillaries. This process is crucial for maintaining fluid balance and preventing edema.

**Why the Correct Answer is Right**
The correct answer involves the contraction of smooth muscle cells in the lymphatic vessels, which is mediated by the myogenic mechanism. The myogenic response is a reflexive contraction of smooth muscle cells in response to increased stretch or pressure, allowing the lymphatic vessels to actively pump fluid into the lymphatic capillaries. This mechanism is essential for the efficient removal of excess fluid from interstitial tissue spaces.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the initial step in lymphatic fluid resorption. While the lymphatic vessels do play a crucial role in fluid removal, the initial step involves contraction and relaxation of smooth muscle cells, not simply the presence of lymphatic vessels.

**Option B:** This option is incorrect because it describes a later step in the lymphatic fluid resorption process. The reabsorption of proteins and other large molecules into the lymphatic capillaries occurs after the fluid has entered the lymphatic vessels, not as the initial step.

**Option C:** This option is incorrect because it describes a different aspect of lymphatic function. The lymphatic vessels do transport lymphocytes and other immune cells, but this is not the primary mechanism for removing excess fluid from interstitial tissue spaces.

**Clinical Pearl / High-Yield Fact**
The myogenic mechanism in lymphatic vessels is essential for maintaining fluid balance and preventing edema, especially in the setting of increased venous pressure or inflammation.

**Correct Answer:** C. Contraction of smooth muscle cells in lymphatic vessels.