Semiquantitative PCR analysis of RAR expression in differentiated granulocytes (Gr-1⁺) and other cell types (Gr-1⁻). Cells were separated as described in Materials and Methods. The PCR reaction was performed for 25 to 35 cycles for RARα1 and RARα2 and 50 cycles for RARγ and RARβ. Shown is a Southern blot analysis of the PCR product hybridized with an internal oligonucleotide probe specific for each amplification product, as described in Materials and Methods.