title: The magnitude of CD4+ T cell recall responses is controlled by the duration of the secondary stimulus.
abstract: The parameters controlling the generation of robust CD4(+) T cell recall responses remain poorly defined. In this study, we compare recall responses by CD4(+) and CD8(+) memory T cells following rechallenge. Homologous rechallenge of mice immune to either lymphocytic choriomeningitis virus or Listeria monocytogenes results in robust CD8(+) T cell recall responses but poor boosting of CD4(+) T cell recall responses in the same host. In contrast, heterologous rechallenge with a pathogen sharing only a CD4(+) T cell epitope results in robust boosting of CD4(+) T cell recall responses. The disparity in CD4(+) and CD8(+) T cell recall responses cannot be attributed to competition for growth factors or APCs, as robust CD4(+) and CD8(+) T cell recall responses can be simultaneously induced following rechallenge with peptide-pulsed dendritic cells. Instead, CD4(+) T cell recall responses are dependent on the duration of the secondary challenge. Increasing the rechallenge dose results in more potent boosting of CD4(+) T cell recall responses and artificially limiting the duration of secondary infection following heterologous rechallenge adversely impacts the magnitude of CD4(+) T cell, but not CD8(+) T cell, recall responses. These findings suggest that rapid pathogen clearance by secondary CTL following homologous rechallenge prevents optimal boosting of CD4(+) T cell responses and therefore have important practical implications in the design of vaccination and boosting strategies aimed at promoting CD4(+) T cell-mediated protection.
authors: Department of Pathology, University of Utah, Salt Lake City, UT 84112, USA.
authors: Eugene V
authors: EV
authors: Ravkov
authors: Matthew A
authors: MA
authors: Williams
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology / Q000276:immunology* / Q000382:microbiology / Q000821:virology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology / Q000382:microbiology / Q000821:virology; D002460:Cell Line; D049109:Cell Proliferation; D006224:Cricetinae; D007117:Immunization, Secondary / Q000379:methods; D007156:Immunologic Memory; D008089:Listeria monocytogenes / Q000276:immunology; D008213:Lymphocyte Activation / Q000276:immunology*; D008217:Lymphocytic choriomeningitis virus / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D010047:Ovalbumin / Q000008:administration & dosage / Q000276:immunology; D013997:Time Factors
chemical_list: D010047:Ovalbumin