Table 3. Histological scoring index.

grade	• Histological appearance
0	• no focal infiltration or peribronchial or perivascular inflammatory infiltrates
1	• cuffs of leukocytes and eosinophils mostly around central bronchi and veins in a thin layer• more lymphocytes than eosinophils
2	• cuffs of leukocytes and eosinophils around central bronchi and veins in a layer thicker than grade 1• lymphocytes/eosinophils ratio: 50/50• no/some aggregates of inflammatory cells in lung parenchyma
3	• cuffs of leukocytes and eosinophils around central bronchi and veins and up to 2/3 of periphery• lymphocytes/eosinophils ratio: 50/50• some aggregates of inflammatory cells in lung parenchyma
4	• cuffs of leukocytes and eosinophils around all visible bronchi and veins up to pleura• eosinophilic cells diffuse in lung parenchyma• aggregates of inflammatory cells diffuse in lung parenchyma

The scoring index was adapted from Mehlhop et al [42] with minor modifications. According to this index, inflammatory infiltrations observed in lung tissues sections (figure 2) were quantified.