Immune complexes in the lung in nonspecific and usual interstitial pneumonia

Purpose: To determine whether or not there is a difference in the prevalence of immune complexes in the lung between subjects with nonspecific interstitial pneumonia (NSIF) and usual interstitial pneumonia (UIP) lung biopsy patterns. Methods: From a subgroup of subjects that had open lung biopsies done for interstitial lung disease at Mayo Rochester between 1976-1985 and that also had immunoflorescent studies for immune complexes (IC), we identified 5 subjects with NSIP and 13 with UIP using recently described criteria (Katzenstein et al. AJRCCM 1998; 157:1301-15). Results: Immunoglobulins were identified in biopsy tissue in 5/5 subjects with NSIP vs 3/13 with UIP (p=0.007). Complement components were present in 4/5 subjects with NSIP vs 2/13 with UIP (p=0.022). There was a trend for younger age at biopsy and more prolonged survival in the NSIP group as opposed to the UIP group. Conclusions: This study does not resolve whether NSIP and UIP are different stages of the same disease, or begin as different diseases. Either hypothesis could explain the tendency for NSIP to be responsive and for UIP to be refractory to immunosuppressive therapy. We believe that our data suggests that idiopathic UIP is not an immune-complex mediated disease in most patients. By contrast, NSIP probably is immunologically mediated in the majority, perhaps reflecting underlying connective-tissue disorders and/or hypersensitivity reactions in the lung. Clinical Implications: Previous workers have reported similar results, in that subjects with cellular patterns at biopsy had a higher probability of having IC present and also had better survival than did those with more fibrotic patterns (Dreisin et al. NEJM 1978; 298:353-7; and Schwarz et al. J Lab Clin Med 1978; 91:929-38). These workers believed that "cellular UIP" (similar to what is now described as NSIP) was an early, potentially reversible stage of a process with immune complexes in the lung, which ultimately became "diffuse fibrosis" (similar to what is now described as idiopathic UIP) with undetectable immune complexes. The results of this study suggest that NSIP may be a different disorder than idiopathic UIP from the outset.