RT-PCR analysis of Fas mRNA in NHLs. A region encompassing exons 7-9 was amplified with primers FAS533 and FAS737 in three lymphoma samples in which mutations had been identified in the acceptor splice site of Fas intron 7 (IVS7nt-2a → g; DLC-B 225), or in the donor splice site of Fas intron 8 (IVS8nt + 5g → a, MALT 146; and IVS8nt + 5g → c, MALT 67). In all three samples, skipping of exon 8 was demonstrated by the occurrence of a shorter band that was not present in RNA isolated from peripheral blood lymphocytes of a normal volunteer (PBL). M, 100-bp ladder.