Unique structure of murine interleukin-2 as deduced from cloned cDNAs

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Abstract
Interleukin-2 (IL-2) is a lymphokine originally described as a humoral factor required for the continued proliferation of activated T-cell clones1,2. It also seems to be involved in the mitogenic response of thymocytes3,4, in augmenting natural killer cell activity5, in the generation of cytotoxic T cells6 and in the induction of other lymphokines such as γ-interferon7,8 and a B-cell growth factor (BCGF-1) 9. More recently, there has been evidence for the involvement of IL-2 per se in the stimulation of B-cell growth (ref. 10 and T. Kishimoto and J. Vilček, personal communications). We have reported previously the cloning and expression of a human IL-2 complementary DNA. The cDNA encodes biologically active IL-2 which would consist of 153 amino acids, including a signal sequence11. Because so much of the work on IL-2 has been done in the human and mouse, we sought to obtain cDNA encoding murine IL-2, and we now report the cloning, expression and sequence analysis of murine IL-2 cDNAs. The longest cDNA insert encodes a polypeptide of 169 amino acids, containing unique repeats of a CAG sequence which would encode 12 consecutive glutamine residues within the active IL-2 molecule.