The most impoant function of epitheliod cells in TB is

ref harsh Mohan 9/e p97 The granuloma contains mostly blood-derived macrophages,epithelioid cells (differentiated macrophages) and multinucleated giant cells (also known as Langhans giant cells), surrounded by T lymphocytes . Caseous granulomas are typical oftuberculosis. ... T cells were then rapidly recruited to the forming granuloma. Epithelioid cells are cells of the mononuclear phagocyte system found in ceain granulomas mainly associated with intense immunological activity. ... It is suggested that "vesicular epithelioid cellscould develop from "secretory" epithelioid cells by a process of degeneration.