An Immunohistochemical Study of Canine Nasal Aspergillosis

In this study, histochemistry and immunohistochemistry were used to characterize the phenotype and distribution of leucocytes in the distal nasal mucosa of 15 dogs with nasal aspergillosis. The most consistent histopathological finding was a severe, predominantly lymphoplasmacytic, inflammatory infiltration of the lamina propria. Fungal hyphae were not observed to invade the mucosa but were found at the mucosal surface and within material collected from the nasal cavity. The main immunohistochemical findings were (1) a predominance of IgG+ plasma cells over IgA+ and IgM+ plasma cells, (2) significant numbers of macrophages and dendritic cells expressing MHC class II molecules, (3) macrophages and neutrophils expressing L1 antigen and (4) a mixture of CD4+ and CD8+ T cells. These findings are consistent with a dominant Th1-regulated cell-mediated immune response. The nature of the inflammatory infiltrate and the lack of invasiveness of the mucosa by the fungus, together with the clinical course of the disease and the apparent immunocompetence of the affected dogs, suggest that canine nasal aspergillosis resembles the chronic erosive non-invasive fungal sinusitis described in human patients.