title: Precursor frequency of antigen-specific T cells: effects of sensitization in vivo and in vitro.
abstract: Limiting dilution analysis (LDA) of primary lymphocyte cultures was used to determine the frequency of keyhole limpet hemocyanin (KLH)-specific precursors in the peripheral blood of unimmunized individuals. The KLH-specific precursor frequencies ranged from 1:150,000 to 1:340,000. In contrast, frequencies of KLH-specific cells in the blood from immune donors ranged from 1:25,000 to 1:42,000. LDA of KLH-stimulated primary cultures indicated that the frequency of KLH-specific cells increased with time in culture reaching a four- to fivefold expansion relative to the frequency obtained prior to culture. The data presented suggest that the enhanced kinetics of secondary T-cell responses observed after in vitro sensitization are due to a decrease in the proportion of lymphocytes which exhibit a suppressor phenotype.
mesh_terms: D000328:Adult; D000941:Antigens / Q000008:administration & dosage* / Q000276:immunology; D002478:Cells, Cultured; D004306:Dose-Response Relationship, Immunologic; D000939:Epitopes / Q000032:analysis*; D006412:Hematopoietic Stem Cells / Q000276:immunology*; D006433:Hemocyanins; D006801:Humans; D007114:Immunization; D007700:Kinetics; D007958:Leukocyte Count; D013299:Streptodornase and Streptokinase / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D000941:Antigens; D000939:Epitopes; D006433:Hemocyanins; D013299:Streptodornase and Streptokinase; C032808:keyhole-limpet hemocyanin