Characterization of the subtracted cDNA library by Northern blot analysis. Sense RNAs were synthesized by the T7 RNA polymerase reaction using the Not I–digested plasmid DNA of the +/+ CMC, mi/mi CMC, and subtracted cDNA libraries as templates. Two micrograms of synthesized RNA was loaded per lane, electrophoresed, transferred, and fixed onto nylon membranes. Probes were prepared from the cDNAs for MMCP-6, MC-CPA, β-actin, or Gr B using the random hexamer labeling method.