Tryptophan-induced lung disease: an immunophenotypic, immunofluorescent, and electron microscopic study.

L-tryptophan (LT) has been implicated as a causal agent in the recently recognized eosinophilia-myalgia syndrome (EMS). Pulmonary complications occur in up to 60% of patients. Lung biopsies have shown chronic interstitial pneumonia, mild eosinophilia, vasculitis and perivasculitis, and hypertensive pulmonary arteriopathy. Open lung biopsies from two women who developed respiratory symptoms associated with LT EMS were studied with a panel of antibodies to lymphoid cells, by transmission electron microscopy and by direct immunofluorescence for immunoglobulin and complement. The majority of the cells infiltrating the interstitium and around vessels were T-cells, with a predominance of CD8+ cells. Numerous alveolar macrophages were also identified. Rare polyclonal B-cells were also present. Ultrastructural studies confirmed the presence of interstitial and perivascular lymphocytes as well as occasional eosinophils. The inflammatory cells were also present in vessel cells. Fibrointimal thickening was not observed in the sections studied ultrastructurally. Immunofluorescent staining for IgG, IgA, C3, C4, albumin, kappa, and lambda was negative. There was scattered staining for fibrinogen in alveolar spaces. The etiology of LT EMS is still under investigation, although a contaminant acting in conjunction with host factors is the favored hypothesis. The results of this study indicate that T cytotoxic/suppressor cells may be intimately involved in the pathogenesis of the lung injury.