Gene isolation with human T lymphocyte probes. Isolation of a gene that expresses an epitope recognized by T cells specific for Mycobacterium bovis BCG and pathogenic mycobacteria.

We have used human CD4+ T lymphocyte clones as primary probes to identify and isolate lambda gt11 rDNA clones that express epitopes recognized by T cells. The method that we describe here permits a direct survey of T cell epitope coding sequences in genomic DNA or cDNA libraries. A lambda gt11 library of Mycobacterium leprae DNA was screened with M. leprae-reactive human T cell clones as probes, allowing the isolation of a M. leprae DNA clone encoding the unidentified Ag. This DNA clone differs in restriction maps from those previously identified by antibody probes and encodes an epitope that is unique to vaccine strains of Mycobacterium bovis bacillus Calmette-Guérin and pathogenic mycobacteria. This method is generally applicable and should expedite the study of Ag and epitopes important to the T cell response in infections and in autoimmune diseases.