Abstract: A wide variety of human cancer cells such as glioma and lymphoma express interleukin-4 receptors(IL-4R), therefore, it may be a good option to treat IL-4R-bearing tumor with IL-4-containing immunotoxins. By software analysis, two important amino acids 13T and 121R of (IL-4) were chosen for site-directed mutation. Interleukin-4 mutein cpIL-4(13D121E) was obtained through overlapping PCR and the chimeric immunotoxin was constructed by fusion of the gene encoding cpIL-4(13D121E) to a gene encoding a modified Pseudomonas exotoxin A(PE38KDEL). The chimeric immunotoxin was expressed in E. coli with the yield of about 30% of the total bacterial protein. After being highly purified by affinity chromatography and anion exchange chromatography, the chimeric protein was tested for its cytotoxicity. The data show that cpIL-4(13D121E)-PE38KDEL had improved cytotoxicity to lymphoma cells Daudi expressing class Ⅰ IL-4R in comparison with other IL-4-containing immunotoxin and had a lower cytotoxicity to endothelial cells expressing class Ⅱ IL-4R.

Key words: Immunotoxin, Interleukin-4(IL-4R), Pseudomonas exotoxin A