Pulmonary granulomas caused experimentally in mice by a recombinant triggerfactor protein of Propionibacterium acnes

Etiology of sarcoidosis remains unknown. Atrigger factor from Propionibacterium acnes causesa cellular immune response in some sarcoidpatients but not in nonsarcoid subjects. We examinedwhether experimentally induced hypersensitivityto the trigger factor gives rise to granulomas.Female C57BL/6 mice primed intravenously with P.acnes or not were sensitized with recombinant-proteinRP35, a fragment of P. acnes trigger factor, andcomplete Freund’s adjuvant. In controls, RP35was replaced with P. acnes or one of two controlproteins. In primed and unprimed mice, pulmonarygranulomas were found in some of themice sensitized with RP35 or P. acnes but in nocontrol-protein-sensitized mice. Detection of pulmonarygranulomas (25-57%) did not differ significantlybetween mice sensitized with RP35 or P.acnes, primed or not. No difference in popliteallymph-node-cell reactivity and serum antibodies tothese two antigens was found between mice withand without pulmonary granulomas. P. acnes wascultured from the lungs of 8 (33%) of 24 untreatedmice. The recombinant trigger-factor protein of P.acnes caused pulmonary granulomas in primedand unprimed mice sensitized with the proteinand adjuvant. Sarcoid granulomas may form duringhypersensitivity to antigens of P. acnes indigenousto the affected organ.