Assessing the replicative history of human T cells.
Upon encountering antigen, T cells clonally expand and differentiate into effector cells that directly or indirectly eliminate antigen-bearing pathogens. When renewed contact with the same pathogen occurs the immune response is mounted in a faster and more accurate way, a process that is referred to as immunological memory. The basis for T-cell memory is at least partially provided by an enhanced precursor frequency of antigen-specific T cells, and an increased responsiveness of primed T cells to activation signals. In contrast to B cells, which acquire mutations in the immunoglobulin genes after antigenic challenge, somatic markers are lacking that distinguish unprimed (or naive) from primed (encompassing memory and effector) T cells. Instead, differential expression of cell surface molecules on subsets of T cells and measures for replicative history can be used to obtain insight into the antigen-driven development of the T-cell compartment. Apart from fundamental issues addressing lineage relationships between naive, memory and effector T cells and the cellular basis for long-term T-cell memory, these types of studies have proved to be valuable in understanding T-cell reconstitution in situations of severe T-cell depletion, i.e., after chemotherapy, treatment with depleting CD4 monoclonal antibodies or during HIV infection.
Van Lier
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Department of Immunobiology, CLB, Academic Medical Centre, Plesmanlaan, Amsterdam, Netherlands. r_van_lier@clb.nl
Baars
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D000367:Age Factors; D000943:Antigens, Differentiation / Q000235:genetics / Q000378:metabolism; D004261:DNA Replication / Q000235:genetics*; D006801:Humans; D007111:Immunity, Cellular / Q000235:genetics; D007113:Immunity, Innate / Q000235:genetics; D007156:Immunologic Memory / Q000235:genetics*; D017493:Leukocyte Common Antigens / Q000276:immunology* / Q000378:metabolism; D013601:T-Lymphocytes / Q000276:immunology*; D020080:Tandem Repeat Sequences
D000943:Antigens, Differentiation; D017493:Leukocyte Common Antigens