FIG. 2.

Photomicrographs of lungs of guinea pigs at 20 days postinfection with the H37Rv strain of M. tuberculosis. (A) Mixed inflammatory cells, including lymphocytes, macrophages, and granulocytes (heterophils and eosinophils), are present in the perilymphatic connective tissue, with early intralesional necrosis (arrow) and granulocyte infiltration (magnification, ×200). (B) Mixed inflammation extends from the periarterial and perilymphatic connective tissue and into the surrounding (arrows) pulmonary parenchyma (magnification, ×100). (C) Higher magnification of the field shown in panel B, demonstrating lymphangitis where the mixed inflammation infiltrates the wall (arrow) of a lymphatic vessel (magnification, ×400). Tissues were stained with H&E.