Expression of IL-11 receptor α chain in single human BM CD41⁺CD14⁻ cells. The lower panels are the ethidium bromide-stained amplified MK cDNAs that were transferred to nylon membranes, probed with the specified receptor cDNAs, and subjected to FUJI bio imaging analysis (upper panels). Five MKs were analyzed for IL-11 receptor α chain expression (A) to avoid individual cell artifacts, and the cell differences may represent heterogeneity in the MK population. The cDNAs were also probed for c-mpl gene expression (B), a receptor known to be MK lineage-specific. K562 cells and HEL cells were used as positive controls for IL-11 receptor α chain and c-mpl expression, respectively. Jurkat cells were used as a negative control for both genes. The amplification protocol produces variable length cDNAs from any given transcript, so that smears rather than bands result when the membranes are hybridized to a corresponding probe.24