The Role of Circulating Soluble CD74 in Acute Lung Injury

Acute lung injury (ALI) or acute respiratory distress syndrome (ARDS) is a devastating cause of morbidity and mortality characterized by alveolar epithelial and endothelial injury. Despite recent advances in pathogenetic mechanisms and therapy strategies of ALI, efforts to identify circulating factors that predict severity of ALI/ARDS patients have been unrevealing.

CD74 (also known as a major histocompatibility complex (MHC) class II invariant chain) is a type II transmembrane protein, recently found to be the high-affinity receptor of macrophage migration inhibitory factor (MIF). MIF promotes neutrophil accumulation in alveolar space via binding to CD74 expressed on the cell surface. Our previous study， consistent with others, has shown that MIF was highly expressed in acute lung injury (ALI). In addition, we also detected highly CD74 expression in lipopolysaccharide (LPS)-induced ALI mouse model. Recently, a circulating form of CD74 was discovered in autoimmune liver disease. Similarly, we investigated the existence of soluble form of CD74 in serum and bronchoalveolar lavage fluid (BALF) in ALI mouse model and burn or trauma related ALI patients. Based on these finds, we postulated that soluble CD74 might participate in regulating lung inflammation and be a potential novel ALI/ARDS biomarker.

Inclusion criteria

• Clinical diagnosis of ALI/ARDS
• Informed consent was obtained from either the subjects themselves or from designated surrogates before enrollment in the study.

Exclusion criteria

• Patients who have chronic lung disease before enrollment.
• Patients who have severe organ dysfunction, autoimmune diseases and tumor.
• Women who are pregnant or breast-feeding.
• Patients who, in the opinion of the Investigator, have any other medical condition which renders the patient unable to complete the study or which would interfere with optimal participation in the study or produce significant risk to the patient.
• Patients participating in or planning to enroll in another clinical trial during the time of the study.