**Core Concept**
Epithelioid cells are a type of transformed macrophage that plays a crucial role in the granulomatous response of tuberculosis. They are characterized by their large size, abundant cytoplasm, and often, a central nucleus. The transformation of macrophages into epithelioid cells is a key feature of tuberculosis pathology.

**Why the Correct Answer is Right**
Epithelioid cells are primarily involved in the secretory function of containing the spread of Mycobacterium tuberculosis. They release various cytokines, chemokines, and other signaling molecules that help to activate the immune response and limit the bacterial spread. This secretory function is essential for the formation of granulomas, which are characteristic of tuberculosis pathology. The release of these molecules also helps to attract other immune cells, such as T lymphocytes and neutrophils, to the site of infection.

**Why Each Wrong Option is Incorrect**
**Option A:** Phagocytosis is a function primarily associated with macrophages, not epithelioid cells. While epithelioid cells do ingest bacteria, their primary function is not phagocytosis.

**Option C:** Antigenic refers to the ability of a substance to induce an immune response. While epithelioid cells do play a role in presenting antigens to T lymphocytes, their primary function is not antigenic.

**Option D:** Healing is a process that involves the resolution of inflammation and tissue repair. While epithelioid cells do contribute to the healing process, their primary function is not healing.

**Clinical Pearl / High-Yield Fact**
Epithelioid cells are a characteristic feature of granulomatous diseases, including tuberculosis and sarcoidosis. The presence of epithelioid cells in tissue biopsy samples is a key diagnostic feature of these conditions.

**✓ Correct Answer: B. Secretory. Epithelioid cells are primarily involved in the secretory function of containing the spread of Mycobacterium tuberculosis.**