Expression of PAF-R mRNA by BMSC. PAF-R was detected on BMSC (lane 2) and monocytic cell line U937 as positive control (lane 3), using specific primers and various amplification cycles as described in Materials and Methods. The base-pair length was determined with marker DNA fragments (lane 1). Lane 4 is the no-template control. β-Actin gene expression was also examined as an internal control to ensure RNA integrity and proper amplification.