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Memory-phenotype CD4+ T cells spontaneously generated under steady-state conditions exert innate TH1-like effector function.

ABSTRACT: Conventional CD4+ T cells are composed of naïve, pathogen-specific memory, and pathogen-independent memory-phenotype (MP) cells under steady state. Naïve and pathogen-specific memory cells play key roles in adaptive immunity, whereas the homeostatic mechanisms regulating the generation of MP cells and their biological functions are unclear. We show that MP cells are autonomously generated from peripheral naïve cells in the absence of infectious stimulation in a T cell receptor (TCR)- and CD28-dependent manner. We further demonstrate that MP cells contain a T-bethi subpopulation that is continuously generated by environmental interleukin-12 (IL-12) and rapidly produces interferon-? (IFN-?) in response to IL-12 in the absence of pathogen recognition. These cells can provide nonspecific host resistance against Toxoplasma gondii infection while enhancing the adaptive CD4+ T cell responses. Together, these findings reveal that MP cells are continuously generated from naïve precursors and have a previously undescribed innate immune function by which they produce an early, T helper cell type 1 (TH1)-like protective response against pathogens.

SUBMITTER: Kawabe T

PROVIDER: S-EPMC5568832 | biostudies-literature | 2017 Jun

REPOSITORIES: biostudies-literature

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Memory-phenotype CD4+ T cells spontaneously generated under steady-state conditions exert innate TH1-like effector function.

Kawabe Takeshi T Jankovic Dragana D Kawabe Shuko S Huang Yuefeng Y Lee Ping-Hsien PH Yamane Hidehiro H Zhu Jinfang J Sher Alan A Germain Ronald N RN Paul William E WE

Science immunology 20170601 12

Conventional CD4+ T cells are composed of naïve, pathogen-specific memory, and pathogen-independent memory-phenotype (MP) cells under steady state. Naïve and pathogen-specific memory cells play key roles in adaptive immunity, whereas the homeostatic mechanisms regulating the generation of MP cells and their biological functions are unclear. We show that MP cells are autonomously generated from peripheral naïve cells in the absence of infectious stimulation in a T cell receptor (TCR)- ...[more]

PMID: 28783663

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Project description:During antiretroviral therapy (ART), human immunodeficiency virus type 1 (HIV-1) persists as a latent reservoir in CD4+ T cell subsets in central memory (TCM), transitional memory (TTM), and effector memory (TEM) CD4+ T cells. We have identified differences in mechanisms underlying latency and responses to latency-reversing agents (LRAs) in ex vivo CD4+ memory T cells from virally suppressed HIV-infected individuals and in an in vitro primary cell model of HIV-1 latency. Our ex vivo and in vitro results demonstrate the association of transcriptional pathways of T cell differentiation, acquisition of effector function, and cell cycle entry in response to LRAs. Analyses of memory cell subsets showed that effector memory pathways and cell surface markers of activation and proliferation in the TEM subset are predictive of higher frequencies of cells carrying an inducible reservoir. Transcriptional profiling also demonstrated that the epigenetic machinery (known to control latency and reactivation) in the TEM subset is associated with frequencies of cells with HIV-integrated DNA and inducible HIV multispliced RNA. TCM cells were triggered to differentiate into TEM cells when they were exposed to LRAs, and this increase of TEM subset frequencies upon LRA stimulation was positively associated with higher numbers of p24+ cells. Together, these data highlight differences in underlying biological latency control in different memory CD4+ T cell subsets which harbor latent HIV in vivo and support a role for differentiation into a TEM phenotype in facilitating latency reversal.IMPORTANCE By performing phenotypic analysis of latency reversal in CD4+ T cells from virally suppressed individuals, we identify the TEM subset as the largest contributor to the inducible HIV reservoir. Differential responses of memory CD4+ T cell subsets to latency-reversing agents (LRAs) demonstrate that HIV gene expression is associated with heightened expression of transcriptional pathways associated with differentiation, acquisition of effector function, and cell cycle entry. In vitro modeling of the latent HIV reservoir in memory CD4+ T cell subsets identify LRAs that reverse latency with ranges of efficiency and specificity. We found that therapeutic induction of latency reversal is associated with upregulation of identical sets of TEM-associated genes and cell surface markers shown to be associated with latency reversal in our ex vivo and in vitro models. Together, these data support the idea that the effector memory phenotype supports HIV latency reversal in CD4+ T cells.

Project description:Naïve CD4 T (NCD4T) cells post-activation undergo programming for inducible production of cytokines leading to generation of memory cells with various functions. Based on cytokine based polarization of NCD4T cells in vitro, programming for either 'Th1' (interferon-gamma [IFNg]) or 'Th2' (interleukin [IL]-4/5/13) cytokines is thought to occur via mutually exclusive expression and functioning of T-bet or GATA-3 transcription factors (TFs). However, we show that a high proportion of mouse and human memory-phenotype CD4 T (MCD4T) cells generated in vivo which expressed either Th1 or Th2 cytokines commonly co-expressed T-bet and GATA-3. While T-bet levels did not differ between IFNg-expressing and IL-4/5/13-expressing MCD4T cells, GATA-3 levels were higher in the latter. These observations were also confirmed in MCD4T cells from FVB/NJ or aged C57BL/6 or IFNg-deficient mice. While MCD4T cells from these strains showed greater Th2 commitment than those from young C57BL/6 mice, pattern of co-expression of TF was similar. Effector T cells generated in vivo following immunization also showed TF co-expression in Th1 or Th2 cytokine producing cells. We speculated that the difference in TF expression pattern of MCD4T cells generated in vivo and those generated in cytokine polarized cultures in vitro could be due to relative absence of polarizing conditions during activation in vivo. We tested this by NCD4T cell activation in non-polarizing conditions in vitro. Anti-CD3 and anti-CD28-mediated priming of polyclonal NCD4T cells in vitro without polarizing milieu generated cells that expressed either IFNg or IL-4/5/13 but not both, yet both IFNg- and IL-4/5/13-expressing cells showed upregulation of both TFs. We also tested monoclonal T cell populations activated in non-polarizing conditions. TCR-transgenic NCD4T cells primed in vitro by cognate peptide in non-polarizing conditions which expressed either IFNg or IL-4/5/13 also showed a high proportion of cells co-expressing TFs, and their cytokine commitment varied depending on genetic background or priming conditions, without altering pattern of TF co-expression. Thus, the model of mutually antagonistic differentiation programs driven by mutually exclusively expressed T-bet or GATA-3 does not completely explain natural CD4 T cell priming outcomes.

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Memory-phenotype CD4+ T cells spontaneously generated under steady-state conditions exert innate TH1-like effector function.

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Memory-phenotype CD4<sup>+</sup> T cells spontaneously generated under steady-state conditions exert innate T<sub>H</sub>1-like effector function.

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