Ficoll separated human PBMC from healthy donors, infected with purified Chlamydia trachomatis EB serovar K (UW/31/Cx) and incubated at 37C at 5% CO2 for 4 h
Extracted molecule
total RNA
Extraction protocol
cells were resuspended in solution D, total RNA was extracted by application of phenol:chloroform 5:1, followed by precipitation in isopropanol at -80°C for 1 hr and incubation with RQ1 DNase at 37 °C for 1 hr.
Label
32P
Label protocol
probes were labeled with 32P using rediprime beats (Amersham)
Hybridization protocol
probes were over night hybridized to a filter-based nylon membrane (Atlas 1.2 I, Clontech)
Scan protocol
signal intensities were retrieved by phosphoimaging using a STORM 860 scanner
Description
cDNA based microarray Messenger RNA of C trachomatis infected monocytes of the three healthy donors was compared with the corresponding mock-infected samples. For mock infection, SPG buffer was used instead of the C trachomatis suspension, all other procedures were performed identically. Cells were resuspended in solution D and total RNA was extracted by application of phenol:chloroform 5:1 (pH 4.5, Ambion, Austin, TX) followed by precipitation in isopropanol at -80°C for 1 hr and incubation with RQ1 DNase (Promega, Madison, WI) at 37 °C for 1 hr. The signal intensity of the G3PDH housekeeping gene on the microarray membrane was used as indirect quality marker for the RNA utilized as only experiments were included in the analysis that revealed a G3PDH signal intensity within 1.5 times the standard deviation of all membranes evaluated in our study. The entire microarray procedure and its analysis has recently been validated and reported in detail. Total RNA of all donors was pooled and for each microarray experiment 150 µg were reverse transcribed and amplified by SMART™-PCR (BD Biosciences Clontech, Palo Alto, CA), a technology that allows reverse transcription of small amounts of total RNA and subsequent amplification of the entire cDNA. Probes were labeled with 32P and subsequently over night hybridized to a filter-based nylon membrane containing immobilized cDNA-specific sequences from a total of 1,184 genes (Human Atlas Array 1.2, BD Biosciences Clontech, Palo Alto, CA). For analysis, we focused solely on the 159 cytokines, chemokines and their receptors as given by the manufacturer. Signal intensities were retrieved by a STORM 860 scanner (Molecular Dynamics, Sunnyvale, CA) in combination with the AtlasImage 2.0 software (BD Biosciences Clontech). Data from all signal intensities were then subtracted by the local background intensity measured around each gene. The local background intensities of all individual genes were subsequently averaged, resulting in the mean background intensity of a particular membrane. Gene expression in our experiments was determined by a spot intensity of a single transcript that exceeded twice the mean background. Normalisation to background and to the G3PDH housekeeping gene was achieved by the global (sum) normalization method. Signal intensity data are given as the ratio of C trachomatis infected vs mock infected probes.
Data processing
data from all signal intensities were subtracted by the local background intensity measured around each gene. The local background intensities of all individual genes were subsequently averaged, resulting in the mean background intensity of a particular membrane. Gene expression in our experiments was determined by a spot intensity of a single transcript that exceeded twice the mean background. Normalisation to background and to the G3PDH housekeeping gene was achieved by the global (sum) normalization method
