中文摘要：

应用RT和RACE-PCR方法获得大鳍鳠（Mystus macrpoterus Bleeker）免疫球蛋白轻链（IgL）2型基因cDNA序列，分析了该基因在组织中的表达。该基因cDNA全长为929 bp，包含5＇非编码区43 bp，3＇非编码区159 bp，开放阅读框720 bp，编码239个氨基酸。编码的氨基酸序列分为可变区（ VL）和恒定区（ CL）。系统进化树分析显示，大鳍鳠IgL蛋白质序列与斑点叉尾 IgL 2型（ G型）合为一支，与其它硬骨鱼类IgL2型聚为一簇。组织分布研究表明，大鳍鳠IgL2基因表达量在脾脏最高，其次是鳃和头肾，这明显与大鳍鳠IgL3型基因表达方式不同。注射嗜水气单胞菌后，大鳍鳠IgL2基因转录表达量在脾脏、鳃和头肾都随时间发生变化。 IgL2基因转录表达量在脾脏4 d就到达高峰，在鳃1 d就达到峰值。这些应答规律与IgL3基因差异显著，推测， IgL2的表达主要参与鳃、肠和皮肤主导的粘膜免疫。

英文摘要：

RT-PCR and Rapid Amplification of cDNA Ends （ RACE） PCR was used to amplify cDNA of immunoglobulin light chain 2 isotype （IgL2） gene from catfish.IgL2 in Myts us macropterus had 929 nucleotides, including 5′-UTR of 43 nucleotides, 3′-UTR of 159 nucleotides and an open reading frame with 720 nucleotides encoding a peptide of 239 amino acids.The deduced amino acid sequence consisted of an constant region （ CL） and a variable domain （ VL）.Phylogenetic tree based on some fish IgL amino acids showed that IgL 2 in M.macropterus was clustered closely with that （ G ） of I.Punctatus.The study on tissue distribution showed that IgL 2 mRNA expression of M.macropterus was mainly detected in spleen,gill and head kidney and increased significantly in these tissues after injection of Aeromonas hydrophila.IgL2 tran-scription level peaked on the4 th day in spleen and on the ist day in gill after bacterin immunization , which was different from that of IgL3 in M.macropterus.The result indicated that IgL2 played a critical role in immunity interaction of mucosa-associated lymphoid tissue （ MALT） in M.macropterus.