Molecular cloning of two CD7 (T-cell leukemia antigen) cDNAs by a COS cell expression system.

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Abstract
The human CD7 antigen (gp40) is a cell surface glycoprotein found on thymocytes and mature T‐cells. It is one of the earliest antigens to appear on cells of the T‐lymphocyte lineage, and the most reliable clinical marker of T‐cell acute lymphocytic leukemia. This report describes the isolation and nucleotide sequence of a full length CD7 cDNA, and of a cDNA for an unusual intron‐bearing precursor. The DNA sequence of the clone predicts a highly glycosylated membrane protein with homology to members of the immunoglobulin superfamily, and no relationship to known oncogenes. Over‐expression of CD7 RNA was observed in only one T‐cell tumor line, and genomic DNA rearrangement was not observed in any lines. Prompted by a recent suggestion that CD7 plays a role in IgM binding, COS cells expressing CD7 were tested and found not to bind IgM or IgM immune complexes.