Summary of the publications

Summary of the publications

2005-2006

Naoki Kobayashi, Takaaki Kondo, Hiroshi Takata, Shumpei Yokota, and Masafumi Takiguchi: Functional and phenotypic analysis of human memory CD8⁺ T cells expressing CXCR3, J. Leukocyte Biol. 80: 320-329, 2006　

Several chemokine receptors play an important role in the migration of naive, memory, and effector T cells. Flow cytometric analyses showed that human CD8⁺ T cells with naive (CD27⁺CD28⁺CD45RA⁺) or memory (CD27⁺- CD28^+/-CD45RA⁺) phenotypes included a population expressing a high level of CXC chemokine receptor 3 (CXCR3^high) and one expressing a low level of it (CXCR3^low), but those with the effector phenotype (CD27^-CD28^-CD45RA^+/-) included a population that did not express CXCR3 (CXCR3^high) and a CXCR3^low population. This relation between the expression level of CXCR3 and memory/effector phenotypes also applied to Epstein-Barr virus- or human cytomegalovirusspecific CD8⁺ T cells. CXCR3^high cells were found predominantly in CC chemokine receptor7 (CCR7)⁺CCR5^- and CCR7^-CCR5^- subsets of CD8⁺ T cells with the CD27⁺CD28⁺CD45RA^- memory phenotype, suggesting that they are memory cells with intermediate differentiation. Indeed, CXCR3^highCD27⁺CD28⁺CD45RA^-- CD8⁺ T cells had the ability to produce interleukin- 2 and interferon-γ. These results together indicate that the expression of CXCR3 is upregulated on intermediately differentiated memory CD8⁺ T cells. CXCR3^highCD8⁺ T cells had a greater ability to migrate in response to CXCR3 ligands than CXCR3^low ones. As CXCR3^high memory CD8⁺ T cells do not express CCR5, high expression of CXCR3 on these memory CD8⁺T cells might play an important role in the migration of these cells to inflammatory sites and in their differentiation.

Center for AIDS Research Best Paper Award 2006
Hiroshi Takata and Masafumi Takiguchi, Three memory subsets of human CD8⁺ T cells differently expressing 3 cytolytic effector molecules. J Immunol 177: 4330-4340, 2006

Multicolor flow cytometric analysis for the expression of three effector molecules, i.e., perforin (Per), granzyme A (GraA), and granzyme B (GraB), in human CD8⁺T cells demonstrated that they included five subpopulations, implying the following pathway for the differentiation of CD8⁺ T cells: Per^-GraA^-GraB^-→Per^-GraA⁺GraB^-→Per^lowGraA⁺GraB^-→ Per^lowGraA⁺GraB⁺→Per^highGraA⁺GraB⁺. The analysis of the expression of these molecules in the subsets classified by the combination of the expression of CCR7 and CD45RA or by that of CD27, CD28, and CD45RA showed that functional CD8⁺ T cell subsets could be partially identified by these phenotypic classifications. However, the functional subsets could be precisely identified by the classification using five cell surface markers or three cell surface markers and three cytolytic molecules. Per^-GraA^-GraB^- and Per^-/lowGraA⁺GraB^- cells were predominantly found in CCR5^-CCR7⁺ and CCR5^high/lowCCR7^- subsets, respectively, of CD8⁺ T cells expressing the CD27⁺CD28⁺CD45RA^- phenotype, whereas Per^low/-GraA⁺GraB^-/+ cells were found in the CCR5lowCCR7^- subset of those expressing this phenotype and in a part of the CCR5^-/lowCCR7^- subset of those expressing the CD27^-/lowCD28^-CD45RA^-/+ phenotype. Ex vivo EBV-specific CD8⁺ T cells, which were Per^low/-GraA⁺GraB^-/+ cells, hardly or very weakly killed the target cells, indicating that these were not effector T cells. These findings suggest that the Per^-GraA^-GraB^-, Per^-/lowGraA⁺GraB^-, and Per^lowGraA⁺GraB⁺ cells were central memory, early effector memory, and late effector memory T cells, respectively. Per^-/lowGraA⁺GraB^- cells gained GraB expression after TCR stimulation, indicating that early effector memory T cells could differentiate into late effector and effector T cells. The present study showed the existence of three memory subsets and the pathway for their differentiation.

Hiroko Tomiyama, Mamoru Fujiwara, Shinichi Oka, and Masafumi Takiguchi: Cutting Edge: Epitope-dependent effect of Nef-mediated HLA class I down-regulation on ability of HIV-1-specific CTLs to suppress HIV-1 replication , J. Immunol 174: 36-40, 2005

It is believed that Nef-mediated HLA class I down-regulation is one of the mechanisms that allow HIV-1-infected cells to escape from being killed by HIV-1-specific human CTLs. In this study, we show that the effect of Nef-mediated HLA class I down-regulation on the ability of HIV- 1-specific CTLs to suppress HIV-1 replication is epitope dependent. The CTLs specific for two Pol epitopes presented by HLA-B*5101, one of the HLA alleles associated with slow progression to AIDS, effectively killed HIV-1- infected CD4 T cells and suppressed HIV-1 replication. In contrast, those specific for the other four epitopes failed to kill HIV-1-infected CD4 T cells and partially or hardly suppressed HIV-1 replication. The difference of the ability between these two types of CTLs may result from the difference of the number of HLA class I epitope complex on the surface of NL-432-infected CD4 T cells.

Mamoru Fujiwara, Hiroshi Takata, Shinichi Oka, Hiroko Tomiyama, and Masafumi Takiguchi, Patterns of cytokine production in HIV-1-specific human CD8+ T cells after stimulation with HIV-1-infected CD4+ T cells, J. Virol. 79: 12536-12543. 2005

Although human immunodeficiency virus type 1 (HIV-1)-specific CD8 T cells can produce various cytokines
that suppress HIV-1 replication or modulate anti-HIV-1 immunity, the extent to which HIV-1-specific CD8 T
cells produce cytokines when they recognize HIV-1-infected CD4 T cells in vivo still remains unclear. We first
analyzed the abilities of 10 cytotoxic T-lymphocyte (CTL) clones specific for three HIV-1 epitopes to produce
gamma interferon, macrophage inflammatory protein 1, and tumor necrosis factor alpha after stimulation
with epitope peptide-pulsed cells. These CTL clones produced these cytokines in various combinations within
the same specificity and among the different specificities, suggesting a functional heterogeneity of HIV-1-
specific effector CD8 T cells in cytokine production. In contrast, the HIV-1-specific CTL clones for the most
part produced a single cytokine, without heterogeneity of cytokine production among the clones, after stimulation
with HIV-1-infected CD4 T cells. The loss of heterogeneity in cytokine production may be explained by
low surface expression of HLA class I?epitope peptide complexes. Freshly isolated HIV-1-specific CD8 T cells
with an effector/memory or memory phenotype produced much more of the cytokines than the same epitopespecific
CTL clones when stimulated with HIV-1-infected CD4 T cells. Cytokine production from HIV-1-
specific memory/effector and memory CD8 T cells might be a critical event in the eradication of HIV-1 in
HIV-1-infected individuals.

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