Abstract: A nucleic acid which can inhibit expression of the MEX3B gene with low cytotoxicity as a side effect, an MEX3B gene expression inhibitor which contains said nucleic acid, a method for inhibiting MEX3B gene expression, and a prophylactic or therapeutic agent for disease caused by MEX3B gene expression are provided. This nucleic acid, which inhibits the expression of the MEX3B gene, is an antisense oligonucleotide having a sequence complementary to an oligonucleotide that contains at least 10 contiguous nucleotides in an untranslated region in an exon of the MEX3B gene, or a double-stranded RNA including at least 20 contiguous nucleotides in the aforementioned untranslated region, or DNA encoding said double-stranded RNA.

Abstract: Provided are a method for screening agents for the prevention or treatment of diseases caused by interleukin 6, interleukin 13, TNF, G-CSF, CXCL1, CXCL2, or CXCL5 and an agent for the prevention or treatment of diseases caused by interleukin 6, interleukin 13, TNF, G-CSF, CXCL1, CXCL2, or CXCL5. A method for screening agents for the prevention or treatment of diseases caused by interleukin 6, interleukin 13, TNF, G-CSF, CXCL1, CXCL2, or CXCL5 having as the index at least one selected from the group consisting of changes in the expression of the MEX3B gene or MEX3B protein and changes in the function of the MEX3B protein.