In all patients small aggregates of macrophages, CD4+ Thelper cells, CD8+ T-cytotoxic cells, CD20+ B-cells, CD1a+ dendritic cells, S100+ dendritic cells, natural killer lymphocytes were present around vessels and bronchioles. Dendritic cells and TNFa were expressed sparsely in macrophages, AECs and endothelial cells, whereas IFNc was expressed in small mononucleated cells in lungs from patients with S-OIV. There was a very strong expression of IL-4, IL-10 and iNOS in small mononucleated cells.