Lack of CD99 expression in HD-derived cell lines. (A) Northern blot analysis for CD99 expression in HD-derived cell lines. RNA samples were prepared from IM9 (I) and three Hodgkin’s cell lines, HDLM-2 (H), KM-H2 (K), and L-428 (L), and examined for the presence of CD99 transcripts. As a loading control, the blot was reprobed with rRNA. (B) Flow cytometric analysis of HD-derived cell lines.