Isolation of Genes Encoding Proteins of Immunological Importance

This chapter focuses on the isolation of lymphokine genes. The chapter describes the general methodological strategies employed to isolate gene clones for important cellular regulatory molecules. The isolation of genes encoding lymphokines has been particularly challenging, requiring recently developed techniques. Lymphokines are typically low-abundance tissue-specific proteins. Therefore, the isolation of genes encoding them is hampered by a corresponding low abundance of their mRNAs: the starting material for synthesizing cDNA clones. Two important developments have increased the efficiency of identifying cDNA clones of lymphokine genes. First, biologically active lymphokines can often be synthesized by the injection of the appropriate mRNAs into Xenopus oocytes. Second, lymphokine activity can often be recovered from cells transfected with lymphokine cDNA clones placed under the regulatory control of a heterologous gene promoter. Thus, highly efficient biological methods have been developed to determine the identity of lymphokine mRNAs and cDNAs.