Abstract: Objective  To clone and express Der f 7 gene of Dermatophagoides farinae, and identify its immunogenicity.  Methods  Total RNA was extracted from D. farinae mites. A reference sequence （Accession No. AY283292） was used to design specific primers. The Der f 7 gene fragment was amplified by RT-PCR, and cloned into pET-32a vector. The recombinant plasmid was transformed into E. coli BL21 （DE3） and induced with IPTG for protein expression. The recombinant protein was purified by Ni2+ chelating affinity chromatography and analyzed by SDS-PAGE and Western blotting.  Results  The Der f 7 gene fragment was about 650 bp, and shared 99% homology with the published one （Accession No. FJ436108）. SDS-PAGE result showed its relative molecular weight （Mr） of 23 000. The recombinant protein showed appropriate combination ability with IgE in sera of mite allergic patients.  Conclusion  Der f 7 gene has been expressed in prokaryotic expression system and shows allergenicity.

Key words: Dermatophagoides farinae, Der f 7, Allergen, Expression, Purification