Interstitial pneumonitis induced in guinea pigs by the antigens of Rhizopus nigricans

Rhizopus nigricans (Rn) is one of the most common members of the Mucorales that produces opportunistic infections and hypersensitivity states. Data concerning experimental induction in guinea pigs of hypersensitivity pneumonitis with a glycoprotein antigen are presented. This antigen was obtained from the mycelial and metabolic products of the cultures and was aerosolized during 12 weeks. The presence of specific antibodies (IgG and/or IgE) was detected by serological techniques; histopathological studies of the lungs showed interstitial infiltrates of macrophages and LTCD8(+) cells, as revealed by the MoAb used. Single non-necrotizing granulomas were characteristic from the tenth week to the end of the experiment. The results from this animal model suggest that hypersensitivity pneumonitis is a typical delayed-type reaction due to chronic contact with the heterologous glycoprotein of Rn. The relation of Rn antigen and the development of occupational diseases of the lung such as malt-worker's lung and wood-trimmer's disease is proposed and discussed.