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. 2020 Dec 3;7:590037. doi: 10.3389/fvets.2020.590037

Figure 2.

Figure 2

Case 1, histopathological features. (A–G) Lungs. (A) The parenchyma exhibits nodular, partly coalescing, non-demarcated granulomatous infiltrates (*) and alveoli that are packed with macrophages (arrows). HE stain. Bar = 100 μm. (B) The infiltrates (*) are dominated by Iba-1+ macrophages/epithelioid cells, and Iba-1+ macrophages are also confirmed to fill alveolar lumina (inset: arrows). Capillaries generally contain abundant monocytes (Iba-1+; arrows), providing evidence of monocyte recruitment into the tissue. Bars = 50 μm. (C) The granulomatous infiltrates (*) contain moderate numbers of disseminated T cells (CD3+). Inset: HE stain of infiltrate. (D) Only scattered B cells (CD45R+) are present in the infiltrate (arrowheads). However, they form lymphocyte aggregates close to bronchi (*: bronchiolar lumen), representing part of the bronchus associated lymphatic tissue (inset; arrowhead: bronchiolar glands). Bars = 50 μm. (E) Closer view of alveoli granulomatous infiltrates resembling accumulations of alveolar macrophages that fill and expand the alveoli (arrow). Adjacent alveolar lumen with edema fluid and individual desquamed alveolar macrophages (arrowhead). Within granulomatous infiltrates, there are abundant large epithelioid cells (top inset: arrowheads) and occasional bi- or tri-nucleated macrophages (bottom inset: arrowheads), but no multinucleated giant cells. HE stains. Bars = 50 μm. (F) Macrophages cells are also found in the exudate that fills the lumen of a small bronchiole (*). HE stain. Bar = 50 μm. (G) Bronchus with granulomatous infiltrate that breaks into the bronchial lumen (*; arrowhead). Immunohistology for Iba-1. Bar = 50 μm. (H,I) Mandibular lymph node. (H) Cortex and paracortex with effacement of the architecture my granulomatous infiltrates, as shown by the extensive infiltration of Iba-1+ macrophages that appear to invade the lymphatic follicles (*). (I) Immunohistology for CD45R confirms the cortical structures as follicles with adjacent granulomatous infiltrates (*). Bars = 50 μm.