In summary, we discovered that CCSP was not only expressed in the cytoplasm but there was also marked immunoreactivity along in the cell membranes of airway Clara cells. This provided the basis of flow cytometry sorting technology for the isolation of CCSP expressing Clara cells from murine lung. We also found that in vitro, CCSP + cells demonstrated stem cell-like features including stem cell marker expression, bronchosphere colony formation and self-renewal ability. Moreover, a subset of labelretaining cells and BASCs were detectable in the CCSP + population in vivo located in the TBs We conclude that Clara cell isolation by FACS is a useful method for investigating Clara cell function and overall pulmonary stem cell research biology. Development of Real-Time PCR Array for Simultaneous Detection of Eight Human Blood-Borne Viral Pathogens BACKGROUND: Real-time PCR array for rapid detection of multiple viral pathogens should be highly useful in cases where the sample volume and the time of testing are limited, i.e. in the eligibility testing of tissue and organ donors. FINDINGS: We developed a real-time PCR array capable of simultaneously detecting eight human viral pathogens: human immunodeficiency virus types 1 and 2 (HIV-1 and -2), hepatitis B virus (HBV), hepatitis C virus (HCV), human T-cell leukemia virus-1 and -2 (HTLV-1 and -2), vaccinia virus (VACV) and West Nile virus (WNV). One hundred twenty (120) primers were designed using a combination of bioinformatics approaches, and, after experimental testing, 24 primer sets targeting eight viral pathogens were selected to set up the array with SYBR Green chemistry. The specificity and sensitivity of the virus-specific primer sets selected for the array were evaluated using analytical panels with known amounts of viruses spiked into human plasma. The array detected: 10 genome equivalents (geq)/ml of HIV-2 and HCV, 50 geq of HIV-1 (subtype B), HBV (genotype A) and WNV. It detected 100–1,000 geq/ml of plasma of HIV-1 subtypes (A – G), group N and CRF (AE and AG) isolates. Further evaluation with a panel consisting of 28 HIV-1 and HIV-2 clinical isolates revealed no cross-reactivity of HIV-1 or HIV-2 specific primers with another type of HIV. All 28 viral isolates were identified with specific primer sets targeting the most conserved genome areas. The PCR array correctly identified viral infections in a panel of 17 previously quantified clinical plasma samples positive for HIV-1, HCV or HBV at as low as several geq per PCR reaction. CONCLUSIONS: The viral array described here demonstrated adequate performance in the testing of donors’ clinical samples. Further improvement in its sensitivity for the broad spectrum of HIV-1 subtypes is under development. Rapid progress and improvement in molecular technologies have allowed researchers to switch from the traditional approaches of virus detection in clinical samples to multiplexing for simultaneous detection of multiple pathogens in a single assay. A number of different PCR based assays for detection and discovery of multiple pathogens have been developed [1] [2] [3] [4] . Detection microarrays are proven to be useful in the identification and discovery of viruses homologous to known species. They have been used to guide the selection of samples for further analysis by sequencing [1] [2] [3] 5] . However, microarrays based on nucleic acid hybridization are too complex in design and performance for the routine donors testing, and exhibit a comparatively low sensitivity of detection, usually around 10021,000 genome copies of target virus per analyzed sample [1] [2] . Several PCR based assays coupled with oligonucleotide microarray technology (so called resequencing arrays) have been designed to allow simultaneous detection or genotyping of a target group of viruses, such as some critical blood-borne pathogens (3 viruses) [6] , respiratory viruses (16-21 viruses) [7] [8] , and respiratory adenoviruses (6 different serotypes) [9] . Such PCR based approach allows increasing the sensitivity of detection down to 10-100 copies of the target RNA or DNA in a sample.