Isolation and characterization of a cDNA encoding a putative cytokine which is induced by stimulation via the CD2 structure on human T lymphocytes.
To define activation-specific sequences in human T lymphocytes, a cDNA library was constructed by subtractive hybridization using resting and stimulated peripheral blood lymphocyte pairs. Stimulation of peripheral blood lymphocytes was achieved by triggering with mitogenic anti-CD2 (T11) monoclonal antibodies. Differential library screening with cDNA probes derived from stimulated vs. resting peripheral blood lymphocytes led to identification of a novel sequence, termed HC21. The predicted primary and secondary structure of HC21 deduced from the translated nucleotide sequence suggest that the gene encodes a secreted protein of 92 amino acids including a 23-residue leader sequence. Northern blot analysis demonstrates that HC21 mRNA is induced in peripheral blood T lymphocytes and interleukin 2-dependent T cell clones within 10 min following stimulation via CD2, while steady-state RNA expression is maximal by 2 h. Although the kinetics of HC21 expression are similar after stimulation via the antigen/major histocompatibility complex receptor (CD3-Ti), CD3-Ti triggering leads to less accumulation of HC21 RNA than CD2 triggering. In contrast, recombinant interleukin 2 does not induce detectable HC21 RNA expression in T cell clones. Transient expression of the HC21 cDNA in COS cells results in a readily detectable protein band in sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of radiolabeled cell supernatants consistent with HC21 encoding a secreted product. Protein sequence analysis reveals a striking homology (up to 76% identity at amino acid level) with other members of a recently described lymphokine family whose functions are yet to be defined.
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Laboratory of Immunobiology, Dana-Farber Cancer Institute, Boston, MA 02115.
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D000595:Amino Acid Sequence; D000818:Animals; D000945:Antigens, Differentiation, T-Lymphocyte / Q000502:physiology*; D001483:Base Sequence; D015152:Blotting, Northern; D015139:Blotting, Southern; D018801:CD2 Antigens; D002522:Chlorocebus aethiops; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics; D006801:Humans; D066298:In Vitro Techniques; D008213:Lymphocyte Activation; D008222:Lymphokines / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D011948:Receptors, Antigen, T-Cell / Q000502:physiology; D011971:Receptors, Immunologic / Q000502:physiology*; D013601:T-Lymphocytes / Q000502:physiology*; D014162:Transfection
D000945:Antigens, Differentiation, T-Lymphocyte; D018801:CD2 Antigens; D008222:Lymphokines; D011948:Receptors, Antigen, T-Cell; D011971:Receptors, Immunologic; D004247:DNA