Text Box: URINARY ß2-MICROGLOBULIN IN INFANTS WITH CHRONIC LUNG DISEASE Nishimaki S1, Shima Y2, Sato M1, Nakajima Y3, An H1, Tateishi I1, Seki K1, Yokota S1 1 Yokohama City University School of Medicine, Yokohama, Japan 2 Katsushika Red Cross Maternity Hospital, Tokyo, Japan 3 Japan Red Cross Medical Center, Tokyo, Japan Objective: It is suggested that an inflammatory response after respiratory insults contributes to the development of CLD, however the role of interferon(IFN)–γ in chronic lung disease(CLD) of premature infants is unknown. We determined urinary ß2-microglobulin (ß2-MG) values which were induced by IFN-γ. Methods: We determined urinary ß2-microglobulin(ß2-MG) values in 20 infants(median gestation; 27 weeks, birth weight; 880 g, age at study; 37 days) who had CLD and 41 infants(28 weeks, 1024 g, 36 days) in whom CLD did not develop. Results: The median ß2-MG was significantly higher in the CLD infants as compared with the infants without CLD(173,583 vs. 60,161 µg/g of creatinine, p < 0.0001). The urinary ß2-MG levels were markedly elevated in two infants required mechanical ventilation and long-dated oxygen therapy because of severe CLD following intra-uterine infection. In contrast, the ß2-MG increased slightly in the infants received mild oxygen therapy because of not serious CLD. Conclusions: We suggest that elevated IFNγ may contribute to the development of CLD and the urinary ß2-MG measurement may be a useful and safe marker for assessing the disease activity of CLD in premature infants. 2503