Results of reverse transcription polymerase chain reaction for the detection of platelet-activating factor receptor (PAFR) in follicular dendritic cells (FDCs) and B lymphocytes. Total RNA was extracted from purified FDCs or B lymphocytes, and PAFR messenger RNA (mRNA) was detected with specific primers (see "Methods"). The figure shows ethidium bromide-stained gel that is representative of two identical experiments. Lane 1 shows DNA ladder; lane 2, negative control (B lymphocytes without reverse transcriptase); lane 3, FDCs; lane 4, human tonsillar B lymphocytes; lane 5, LA350 B-lymphocyte cell line. Both sources of B lymphocytes have a much stronger mRNA signal than the FDCs have. Equal lane loading was verified by using 3-actin as a housekeeping gene (not shown).