Helper T cell memory: more questions than answers.
The critical participation of helper T cells in immunologic memory of animals is clear. Features of antigen-specific CD4 memory cells in primed animals that distinguish them from naive cells are their increased frequency, their ability to secrete lymphokines in addition to IL-2 and their expression of distinct arrays of surface molecules. The latter include increased CD44, CD45RO, LFA-3 and VLA-4 and decreased CD45RA,B and Mel-14. These differences in surface markers may contribute to increased interaction potential for APC, and to distinct patterns of recirculation, but direct demonstrations of the former have yet to be provided. Other possible distinctions that are also largely hypothetical, include distinct requirements for activation and the ability to respond more rapidly to stimulation. The factors that regulate the development of memory helper T cells are also unknown.
Department of Biology, University of California, San Diego, La Jolla 92093-0063.
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Swain
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Bradley
D000818:Animals; D000941:Antigens / Q000276:immunology; D015703:Antigens, CD / Q000032:analysis; D015704:CD4 Antigens / Q000032:analysis; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D015815:Cell Adhesion Molecules / Q000032:analysis; D006649:Histocompatibility Antigens / Q000032:analysis; D006801:Humans; D007108:Immune Tolerance; D007156:Immunologic Memory; D017493:Leukocyte Common Antigens; D008213:Lymphocyte Activation; D008222:Lymphokines / Q000378:metabolism; D051379:Mice; D008954:Models, Biological; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology* / Q000378:metabolism
D000941:Antigens; D015703:Antigens, CD; D015704:CD4 Antigens; D015815:Cell Adhesion Molecules; D006649:Histocompatibility Antigens; D008222:Lymphokines; D017493:Leukocyte Common Antigens