Mononuclear-cell pulmonary vasculitis in NZB/W mice. I. Histopathologic evaluation of spontaneously occurring pulmonary infiltrates.

This report describes the spontaneous occurrence of pulmonary vasculitis in NZB/W mice, a well-characterized autoimmune strain of mice. These mice develop pulmonary vasculitis in an age-related fashion. Mild perivascular and peribronchiolar lymphoid hyperplasia is first seen at 4 months of age and progresses into severe hyperplasia by 8 months. This precedes the development of angiodestructive lesions, which are first noticeable at 10 months. By 12 months of age all mice show multilobe disease characterized by transmural infiltration of the vascular walls by plasma cells, histiocytes, and mature lymphocytes. Mitotic figures and necrosis are rare to absent. Vessel lumens are markedly narrowed and obliterated in severe cases, with focal disruption of the limiting elastic membranes. In mice older than 10 months of age, there is extension of the infiltrate into the interstitium in a manner similar to that of lymphoid interstitial pneumonia. Arteries and veins are equally affected. The cellular infiltrates and pattern of involvement bears similarity to various pulmonary vasculitides in humans. This is the first report of spontaneous pulmonary vasculitis in NZB/W mice.