title: Double fluorochrome analysis of human bone marrow lymphoid cells: studies with terminal transferase and anti-T-cell monoclonal antibodies.
abstract: Mature thymus-derived (T) lymphocytes are generally believed to be derived from a bone marrow progenitor cell. Data from studies with animals suggest that the enzyme terminal deoxynucleotidyl transferase (Tdt) is expressed in many T-cell progenitors in bone marrow. In this study we attempted to identify Tdt+ bone marrow cells in man that may be committed to T lineage based on coexpression of Tdt and antigens that have previously been useful in characterization of thymocytes or peripheral-blood T cells. We used a panel of ten monoclonal antibodies against such antigens to analyze Tdt+ bone marrow cells using two-color immunofluorescence. We found that T-cell-associated antigens were not expressed on Tdt+ bone marrow cells and that T cells in bone marrow have a phenotype similar if not identical to peripheral-blood T cells. These results support the hypothesis that many postthymic immunocompetent T cells are found in human marrow. Our results also suggest that if Tdt+ bone marrow cells are committed to T lineage, then the acquisition of mature T-cell-associated antigens is an intrathymic event.
mesh_terms: D000293:Adolescent; D000328:Adult; D000911:Antibodies, Monoclonal / Q000276:immunology*; D000954:Antigens, Surface / Q000032:analysis; D001854:Bone Marrow Cells; D002648:Child; D002675:Child, Preschool; D004253:DNA Nucleotidylexotransferase / Q000378:metabolism*; D004254:DNA Nucleotidyltransferases / Q000378:metabolism*; D005456:Fluorescent Dyes; D006801:Humans; D007223:Infant; D013234:Stem Cells / Q000166:cytology / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D000954:Antigens, Surface; D005456:Fluorescent Dyes; D004254:DNA Nucleotidyltransferases; D004253:DNA Nucleotidylexotransferase