Fig. 5

Presence of activated mast cells and macrophages in the testis parenchyma of COVID-19 critically ill patients. a Toluidine blue staining showing an elevated number of mast cells (arrows) in testis parenchyma (scale bar = 50 μm). b In some regions, mast cells were identified inside the seminiferous tubules (red arrow). c Number of mast cells counted in 15 fields of testis parenchyma at × 400 magnification (t-test; two-tailed; infected groups vs control; *p < 0.05). d–g Immunostaining for chymase in testes of control and COVID-19 patients. Activated mast cells (arrows) were observed in COVID-19 patients only (scale bars = 50 μm). d’ Negative control (scale bars = 50 μm). h Heat map of the evaluated genes related to the mast cells and macrophages. The colors compare COVID-19 patients to controls. Green: lower expression than controls. Red: higher expression than controls. i–l Immunostaining for CD68 in testes of control and COVID-19 patients, illustrating the high prevalence of this cell in the deceased patients (scale bars = 50 μm). i’ Negative control (scale bars = 50 μm). m–o PAS-positive monocytes (red arrow) and macrophage (green arrow) indicating their activation (scale bars = 15 μm). o’ PAS-negative cells in the interstitial cells of a control patient (scale bar = 10 μm). p Number of macrophages counted in 10 fields of testis parenchyma at × 400 magnification (t-test; two-tailed; infected groups vs control; *p < 0.05). q N-acetylglucosaminidase (NAG) assay indicating the activation of macrophages in COVID-19 patients’ testes (t-test; two-tailed; control vs infected group; p > 0.05). r–v Immunostaining for CD3 and lymphocyte number in testes of control and COVID-19 patients (t-test; two-tailed; infected groups vs control; *p < 0.05) (scale bars = 50 μm). r’ Negative control (scale bars = 50 μm). x–w Neutrophils and their activity (s: MPO assay) in testis parenchyma (t-test; two-tailed; control vs infected group; p > 0.05) (scale bar = 10 μm). Individual values can be found at https://doi.org/10.6084/m9.figshare.16777786.v8