Fig. 2

Histological sections of bronchial lymph nodes showing the four stages of granulomas from naturally infected beef cattle with bovine tuberculosis. (a): Stage I granuloma, epithelioid cell (green arrow), and multinucleated giant cells (arrowheads) surrounded by lymphocytes (arrows). (Hx & E. Bar = 50 μm). (b): Stage II granuloma (solid), increased numbers of epithelioid macrophages can be seen, encircled by thin layer of C.T. (arrows), and central caseous necrosis is not formed (Hx & E, Bar = 100 μm). (c): Stage III granuloma showing fully formed C.T. (arrows) and central caseated area (asterisk) with little mineralization (Hx& E, Bar = 100 μm). (d): Stage IV granuloma with an extensive central caseated area, mature C.T capsule, and extensive multiple mineralizations (arrows) (Hx& E, Bar = 200 μm). (e): Intracellular acid-fast bacilli present inside the multinucleated giant cell (ZN stain) (arrowhead). (f): a large number of acid-fast bacilli (arrows) were detected in the center necrotic area of the granuloma