RT-PCR analysis of defensin expression by 16HBE cells exposed to A. fumigatus organisms in the presence of different serums. 16HBE human epithelial bronchial cells (5 × 106) were grown in six well plates for 24 hours. The cells were then exposed to the different morphotypes of A. fumigatus or the latex beads in the presence of either Human (HS) or Fetal Calf Serum (FCS), (heated or not at 56°C). After 18 hours of incubation, the cells were washed with PBS, mRNA was isolated by TRIzol Reagent, and RT-PCR was performed as described above in Materials and Methods. Specific primer pairs (Table 1) were used for RNA amplification. The sizes of amplified products are indicated and were as predicted. All products were amplified according to the conditions described in Table 1. Cells were cultivated in a control well in the absence of A. fumigatus. GAPDH was uniformly expressed. One of the four results is shown.