Initial Antigen Encounter Programs CD8+ T Cells Competent to Develop into Memory Cells That Are Activated in an Antigen-Free, IL-7- and IL-15-Rich Environment This information is current as of September 26, 2021. Roberto Carrio, Oliver F. Bathe and Thomas R. Malek J Immunol 2004; 172:7315-7323; ; doi: 10.4049/jimmunol.172.12.7315 http://www.jimmunol.org/content/172/12/7315 Downloaded from References This article cites 52 articles, 26 of which you can access for free at: http://www.jimmunol.org/content/172/12/7315.full#ref-list-1 http://www.jimmunol.org/ Why The JI? Submit online. • Rapid Reviews! 30 days* from submission to initial decision • No Triage! Every submission reviewed by practicing scientists • Fast Publication! 4 weeks from acceptance to publication by guest on September 26, 2021 *average Subscription Information about subscribing to The Journal of Immunology is online at: http://jimmunol.org/subscription Permissions Submit copyright permission requests at: http://www.aai.org/About/Publications/JI/copyright.html Email Alerts Receive free email-alerts when new articles cite this article. Sign up at: http://jimmunol.org/alerts The Journal of Immunology is published twice each month by The American Association of Immunologists, Inc., 1451 Rockville Pike, Suite 650, Rockville, MD 20852 Copyright © 2004 by The American Association of Immunologists All rights reserved. Print ISSN: 0022-1767 Online ISSN: 1550-6606. The Journal of Immunology Initial Antigen Encounter Programs CD8؉ T Cells Competent to Develop into Memory Cells That Are Activated in an Antigen-Free, IL-7- and IL-15-Rich Environment1 Roberto Carrio,* Oliver F. Bathe,† and Thomas R. Malek2* Although much is known concerning the immunobiology of CD8؉ T memory cells, the initial events favoring the generation of CD8؉ T memory cells remain poorly defined. Using a culture system that yields memory-like CD8؉ T cells, we show that 1 day after Ag encounter, Ag-activated T cells developed into memory-like T cells, but this optimally occurred 3 days after Ag encounter. Key phenotypic, functional, and molecular properties that typify central memory T cells were expressed within 48 h when the activated CD8؉ T cells were cultured with IL-7 or IL-15 in the absence of Ag or following transfer into normal mice. These data support a model whereby Ag activation of naive CD8؉ T cells not only programs effector cell expansion and contraction but the Downloaded from potential to develop into a memory cell which ensues in an Ag-free environment containing IL-7 or IL-15. The Journal of Immunology, 2004, 172: 7315–7323. ver the last several years there has been progress in de- Current data favor a linear differentiation model for memory cell fining features that typify the induction of a CD8ϩ T cell development. The main tenet in this model is that memory CD8ϩ immune response, including the production of long- T cells are direct descendants of effector CTL. Thus, after Ag- O ϩ ϩ http://www.jimmunol.org/ lived Ag-specific CD8 T memory cells (1). Upon an initial en- activated naive CD8 T cells expand and differentiate into CTL, counter with Ag, naive CD8ϩ T cells undergo programmed ex- some of these effector cells escape apoptosis and differentiate over pansion, followed by differentiation into effector CTL, and then several weeks to fully express properties of central memory cells. programmed contraction through apoptosis (2–5). Ag-activated This process is complex, requiring the regulation of many genes ϩ CD8 T cells that escape apoptosis go on to differentiate into (26) and optimally occurs after Ag clearance. However, it is still memory cells that are detected in vivo long after the initial Ag unclear at what point effector cells optimally acquire competency ϩ encounter (6–12). The long-term persistence of memory CD8 T to develop into memory cells. This issue is difficult to study in vivo cells depends upon constant slow turnover mediated by IL-7 and during an immune response, as the magnitude of the expansion of IL-15 (10–17). However, very little is known concerning signals the effector CTL potentially obscures the initial emergence of by guest on September 26, 2021 that favor memory cell development. Understanding the nature of memory cells. Typically, memory cell development in this setting such signals is fundamental toward improving the efficacy of has been assessed only after the contraction of effector cells, where vaccines. the detection of memory-like T cells becomes practical. ϩ Two types of memory CD8 T cells have been identified. One The inherent complexity of investigating memory cell develop- is designated effector-memory cells as they exhibit phenotypic and ment solely in vivo as a consequence of Ag activation of naive functional properties similar to effector CTL, but persist after Ag Ag-specific precursor cells accentuates a need for other experi- clearance, predominately in nonlymphoid tissue. The other is mental systems, including in vitro models, that simplify and em- called central memory cells, which are primarily found in second- ulate one or more aspects of memory cell development. There is ary lymphoid tissue and are functionally and phenotypically dis- especially a need for more flexibility in investigating the impact of tinct from effector CTL, effector-memory cells, and naive T cells individual agents or conditions on the cellular and molecular basis (18, 19). Characteristic properties of central memory cells include ϩ of T cell memory. In this regard, we previously demonstrated that expression of CD44high, CD62Lhigh, IL-2R␤ , Ly-6Chigh, and ϩ ϩ short-term (4–5 days) in vitro Ag-activated CD8 T cells readily CCR7 and enhanced sensitivity to Ag that leads to a rapid rein- developed into persistent central memory cells upon adoptive duction of the effector program (20–24). Recent studies indicate transfer into normal syngeneic mice in the absence of Ag (24). that effector-memory cells eventually convert to central memory This approach directly permits assessing the development of mem- cells which have the greatest potential to persist in vivo (25). ory cells from effector cells without complication of an ongoing immune response. Furthermore, von Andrian and colleagues (17, 27) demonstrated that T cells with properties of central memory cells were obtained when Ag-activated CD8ϩ T cells were cul- *Department of Microbiology and Immunology, University of Miami School of Med- icine, Miami, FL 33101; and †Department of Surgery and Oncology, Tom Baker tured for an extended time with IL-15, a cytokine already impli- Cancer Center, University of Calgary, Calgary, Canada cated in regulating the homeostasis of memory CD8ϩ T cells. Received for publication November 19, 2003. Accepted for publication April 9, 2004. These experiments illustrate the ability to model memory cell de- The costs of publication of this article were defrayed in part by the payment of page velopment solely in vitro. charges. This article must therefore be hereby marked advertisement in accordance In the present study, we have refined an in vitro system that with 18 U.S.C. Section 1734 solely to indicate this fact. leads to the generation of central memory-like CD8ϩ T cells. By 1 This research was supported by National Institutes of Health Grant R01 AI40114. using this system, we evaluated the competency of effector CTL to 2 Address correspondence and reprint requests to Dr. Thomas R. Malek, Department of Microbiology and Immunology (R138), University of Miami School of Medicine, develop into memory T cells. Our data support the view that CTL P.O. Box 016960, Miami, FL 33101. E-mail address: [email protected] optimally develop into central memory cells in the absence of Ag Copyright © 2004 by The American Association of Immunologists, Inc. 0022-1767/04/$02.00 7316 INDUCTION OF CD8ϩ MEMORY T CELLS IN VITRO during a discrete time frame and that some changes toward the Proliferation assay memory phenotype are induced within days. IL-7 was shown to be Ag-driven proliferation was determined essentially as previously described as efficient as IL-15 in promoting memory phenotypic cells. These (33). In brief, to measure Ag-driven proliferation, naive OT-I spleen cells ϩ data support a model whereby Ag activation of naive CD8 T cells (1 ϫ 105 cells/well), or cytokine-expanded OT-I T cells (2 ϫ 104/well) not only programs effector cell expansion and contraction but the with T-depleted mitomycin C-treated normal C57BL/6 spleen cells (8 ϫ 104cells/well), as a source of APC, were cultured in 96-well plates with potential to develop into memory cells, which ensues in an Ag-free 3 OVA257–264 (0.1 nM). [ H]Thymidine was added during the last4hofa environment containing IL-7 or IL-15. This latter finding raises the 48-h culture. possibility that IL-7 and IL-15 not only promote the survival and homeostasis of CD8ϩ T memory cells but also instruct aspects of Adoptive transfer a developmental program that typifies these cells. The indicated population of cultured OT-I T cells (10 ϫ 106 cells) was injected via the tail vein in 0.5 ml of HBSS into nonirradiated mice. Materials and Methods mRNA analysis Mice Apoptosis and cell cycle gene expression array systems were purchased OT-I TCR-transgenic mice (28) were maintained by breeding heterozygous from SuperArray Bioscence (Frederick, MD). Total RNA was extracted OT-I mice to wild-type C57BL/6J mice. B6.SJL-Ptprc/BoAiTac mice, con- from the indicated cell population with TRIzol (Life Technologies, Grand genic for CD45 and expressing the CD45.1 allele were purchased from Island, NY). cDNA was prepared from this total RNA and hybridized to Taconic Farms (Germantown, MD). C57BL/6J mice were purchased from the arrayed filters according to the manufacturer’s instruction.