IL-4 expression is not induced in c-Maf–expressing cell lines. (A) IL-4 mRNA is not induced on c-Maf protein expression. RT-PCR analysis of cDNA templates from induced CB6 vector control (lanes 1, 3, 6, and 8) or c-Maf-containing clone 6 (c-Maf, lanes 2, 4, 7, and 9) using primer pairs detecting β-actin control (lanes 1 and 2), IL-4 (lanes 3 to 5), MafG (lanes 6 and 7), or c-Maf (lanes 8 and 9). M, marker lanes; +, IL-4 positive control DNA template. (B) IL-4 neutralizing antibodies do not affect c-Maf–induced monocytic differentiation. Neutralizing antibodies directed against IL-4 or isotype-matched control antibodies were added to cultures of HL-60 c-Maf clone 6 cells at the time of zinc induction. Top row: Wright-Giemsa stain; bottom row: monocyte-specific ANB esterase stain of cytospin preparations.