Polymorphisms in the promoter of the tumor necrosis factor alpha (TNFα) gene have been reported to affect the transcription rate and the release of this cytokine. Among the best studied, the −238 and −308 polymorphisms have been associated with an increased transcriptional activity and TNFα release, whereas the −863 polymorphism have been associated with a reduced transcriptional activity. A growing body of evidence indicates that these polymorphisms may affect susceptibility to different diseases. Here we describe a method to detect the −238, −308, and −863 TNFα polymorphisms by the polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) analysis. Briefly, DNA is amplified by PCR using mutagenic primers containing a single base-pair mismatch adjacent to the polymorphic site to introduce a restriction site into the wild-type nucleotide sequences after amplification. The PCR products are then digested with specific restriction enzymes and analyzed by agarose gel electrophoresis.
