Characterization of lymphocyte populations in nonspecific interstitial pneumonia*

STUDY OBJECTIVES Nonspecific interstitial pneumonia (NSIP) has been identified as a distinct entity with a more favorable prognosis and better response to immunosuppressive therapies than usual interstitial pneumonia (UIP). However the inflammatory profile of NSIP has not been characterized. DESIGN Using immunohistochemistry techniques on open lung biopsy specimens, the infiltrate in NSIP was characterized in terms of T and B cells, and macrophages, and the T cell population further identified as either CD4 (helper) or CD8 (suppressor-cytotoxic) T cells. The extent of Th1 and Th2 cytokine producing cells was determined and compared to specimens from patients with UIP. RESULTS In ten NSIP tissue samples 41.4 +/- 4% of mononuclear cells expressed CD3, 24.7 +/- 1.8% CD4, 19.1 +/- 2% CD8, 27.4 +/- 3.9% CD20, and 14.3 +/- 1.6% had CD68 expression. Mononuclear cells expressed INFgamma 21.9 +/- 1.9% of the time and IL-4 in 3.0 +/- 1%. In contrast, biopsies from eight patients with UIP demonstrated substantially less cellular staining for either cytokine (INFgamma; 4.6 +/- 1.7% and IL-4; 0.6 +/- 0.3%). Significant populations of CD20 positive B-cells were also identified. CONCLUSION The lymphocytic infiltrate in NSIP is characterized by an elevated CD4/CD8 T-cell ratio, and is predominantly of Th1 type, with additional populations rich in B-cells. Such features are consistent with the favorable clinical course observed in patients with NSIP compared to UIP.