title: Virus-specific CD4(+) memory-phenotype T cells are abundant in unexposed adults.
abstract: Although T cell memory is generally thought to require direct antigen exposure, we found an abundance of memory-phenotype cells (20%-90%, averaging over 50%) of CD4(+) T cells specific to viral antigens in adults who had never been infected. These cells express the appropriate memory markers and genes, rapidly produce cytokines, and have clonally expanded. In contrast, the same T cell receptor (TCR) specificities in newborns are almost entirely naïve, which might explain the vulnerability of young children to infections. One mechanism for this phenomenon is TCR cross-reactivity to environmental antigens, and in support of this, we found extensive cross-recognition by HIV-1 and influenza-reactive T lymphocytes to other microbial peptides and expansion of one of these after influenza vaccination. Thus, the presence of these memory-phenotype T cells has significant implications for immunity to novel pathogens, child and adult health, and the influence of pathogen-rich versus hygienic environments.
authors: Division of Immunology and Rheumatology, Stanford University School of Medicine, Stanford, CA 94304, USA.
authors: Laura F
authors: LF
authors: Su
authors: Brian A
authors: BA
authors: Kidd
authors: Arnold
authors: A
authors: Han
authors: Jonathan J
authors: JJ
authors: Kotzin
authors: Mark M
authors: MM
authors: Davis
mesh_terms: D000328:Adult; D000595:Amino Acid Sequence; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology* / Q000473:pathology; D049109:Cell Proliferation; D002648:Child; D002999:Clone Cells; D015658:HIV Infections / Q000276:immunology* / Q000473:pathology / Q000821:virology; D015497:HIV-1 / Q000276:immunology; D006801:Humans; D007156:Immunologic Memory; D016130:Immunophenotyping; D007231:Infant, Newborn; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology; D007252:Influenza Vaccines / Q000276:immunology; D007251:Influenza, Human / Q000276:immunology* / Q000473:pathology / Q000517:prevention & control* / Q000821:virology; D008969:Molecular Sequence Data; D010455:Peptides / Q000276:immunology; D010641:Phenotype; D011948:Receptors, Antigen, T-Cell / Q000235:genetics / Q000276:immunology; D037182:T-Cell Antigen Receptor Specificity; D014611:Vaccination
chemical_list: D007252:Influenza Vaccines; D010455:Peptides; D011948:Receptors, Antigen, T-Cell
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