Expression of chemokine receptors during monocyte differentiation. (A) RNA-PCR assay; 1 μg of total RNA extracted from monocytes at different stages of differentiation (day 1, 3, and 7) was retrotranscribed and amplified as described in Materials and Methods. Porphobilinogen deaminase was used as internal control. Results are representative of 4 independent experiments. (B,C) RNase protection assay; 5 μg of total RNA extracted after 1 and 7 days of monocytes culture was hybridized to the hCR5 multiprobe (P) as described in Materials and Methods. Autoradiographs were exposed for 24 hours (B) or 4 days (C) to better visualize the CCR2 mRNA isoforms. Representative results from 6 independent experiments are shown.