Uteroglobin/CCSP is expressed specifically in the Clara cells. This allows the gene to be used as a marker to identify the elements regulating the physiologic and cell-specific expression of this gene. The regulation of UG/CCSP by IFN-gamma was shown to be at the level of the proximal promoter by the upregulation of HNF3 beta. This has allowed the determination of the factors responsible for the expression of UG/CCSP.