Biomedical subjects

Matthew F Mescher

Publications and source records attributed to Matthew F Mescher.

15 recordsLinked to original sources

PubMed2006

Signals required for programming effector and memory development by CD8+ T cells.

Stimulation of naïve CD8+ T cells with antigen and costimulation results in proliferation and weak clonal expansion, but the cells fail to develop effector functions and are tolerant long term. Initiation of the program leading to the strong expansion and development of effector functions and memory requires a third signal that can be provided by interleukin-12 (IL-12) or interferon-alpha (IFN-alpha). CD4+ T cells condition dendritic cells (DCs) to effectively present antigen to CD8+ T cells, and this conditioning involves, at least in part, CD40-dependent upregulation of the production of these signal 3 cytokines by the DCs. Upon being fully activated, the cytotoxic T lymphocytes develop activation-induced non-responsiveness (AINR), a form of split anergy characterized by an inability to produce IL-2 to support continued expansion. If antigen remains present, IL-2 provided by CD4+ T cells can reverse AINR to allow further expansion of the effector population and conversion to responsive memory cells following antigen clearance. If IL-2 or potentially other proliferative signals are not available, persistent antigen holds cells in the AINR state and prevents the development of a responsive memory population. Thus, in addition to antigen and costimulation, CD8+ T cells require cytokine signals at distinct stages of the response to be programmed for optimal generation of effector and memory populations.

Animals↗

PubMed2005

Signal 3 tolerant CD8 T cells degranulate in response to antigen but lack granzyme B to mediate cytolysis.

Naive CD8 T cells that respond in vivo to Ag and costimulation in the absence of a third signal, such as IL-12, fail to develop cytolytic function and become tolerized. We show in this study that CD8 T cells purified from TCR transgenic mice and stimulated in vitro in the presence or absence of IL-12 form conjugates with specific target cells, increase intracellular Ca2+, and undergo degranulation to comparable extents. Perforin is also expressed at comparable levels in the absence or presence of a third signal, but expression of granzyme B depends upon IL-12. Levels of granzyme B also correlate strongly with the cytolytic activity of cells responding in vivo. In contrast, an increase in CD107a (lysosomal-associated membrane protein 1) expression resulting from degranulation cannot distinguish in vivo generated lytic effector cells from tolerized, noncytolytic cells. Thus, it appears that cells rendered tolerant as a result of stimulation in the absence of a third signal fail to lyse target cells because they are "shooting blanks."

Animals↗

PubMed2005

CD4 T cell-dependent conditioning of dendritic cells to produce IL-12 results in CD8-mediated graft rejection and avoidance of tolerance.

Rejection of ectopic heart transplants expressing OVA requires OVA-specific CD4 and CD8 T cells. In the absence of CD4 T cells, OVA-specific CD8 T cells proliferate and migrate to the graft, but fail to develop cytolytic functions. With CD4 T cells present, clonal expansion of the CD8 T cells is only marginally increased but the cells now develop effector functions and mediate rapid graft rejection. In the presence of CD4 T cells, Ag and B7 levels do not increase on dendritic cells but IL-12 production is up-regulated, and this requires CD154 expression on the CD4 T cells. OVA-specific CD8 T cells lacking the IL-12 receptor fail to differentiate or mediate graft rejection even when CD4 T cells are present. Thus, CD4 T cells condition dendritic cells by inducing the production of IL-12, which is needed as the "third signal" for CD8 T cell differentiation and avoidance of tolerance.

Actins↗

PubMed2005

Type I IFNs provide a third signal to CD8 T cells to stimulate clonal expansion and differentiation.

In this study, we show that IFN-alpha beta can have a direct role in linking innate and adaptive responses by providing the "third signal" needed by naive CD8 T cells responding to Ag and costimulatory ligands. Stimulation of CD8 T cells in the absence of a third signal leads to proliferation, but clonal expansion is limited by poor survival and effector functions do not develop. We show that IFN-alpha beta can provide the third signal directly to CD8 T cells via a STAT4-dependent pathway to stimulate survival, development of cytolytic function, and production of IFN-gamma. Provision of the third signal by either IFN-alpha beta or IL-12 results in regulation of the expression of a number of genes, including several that encode proteins critical for effector function.

Animals↗

PubMed2005

Cutting edge: Bcl-3 up-regulation by signal 3 cytokine (IL-12) prolongs survival of antigen-activated CD8 T cells.

Clonal expansion of T cells requires cell division and survival during the proliferative phase of the response. Naive murine CD8 T cells responding to Ag and costimulation undergo an abortive response characterized by impaired clonal expansion, failure to develop effector functions, and long-term tolerance. A third signal provided by IL-12 is required for full expansion, activation, and establishment of memory. The enhanced survival, and thus clonal expansion, supported by IL-12 is not due to increased Bcl-2 or Bcl-x(L) expression; both are maximally activated by signals 1 and 2. In contrast, Bcl-3, recently shown to enhance survival when ectopically expressed in T cells, is increased only when IL-12 is present. Furthermore, examination of Bcl-3-deficient CD8 T cells demonstrates that the increased survival caused by IL-12 depends upon Bcl-3. The time courses of expression suggest that Bcl-2 and Bcl-x(L) promote survival early in the response, whereas Bcl-3 acts later in the response.

Adjuvants, Immunologic↗

PubMed2004

Artificial antigen-presenting constructs efficiently stimulate minor histocompatibility antigen-specific cytotoxic T lymphocytes.

Cytotoxic T lymphocytes (CTLs) specific for hematopoietic-restricted minor histocompatibility antigens (mHags) are important reagents for adoptive immunotherapy of relapsed leukemia after allogeneic stem cell transplantation. However, expansion of these CTLs to therapeutic numbers is often hampered by the limited supply of antigen-presenting cells (APCs). Therefore, we evaluated whether cell-sized latex beads coated with HLA/mHag complexes HLA-A2/HA-1 or HLA-A2/HA-2 and recombinant CD80 and CD54 molecules can replace professional APCs. The artificial antigen-presenting constructs (aAPCs) effectively stimulated HA-1- and HA-2-specific CTL clones as shown by ligand-specific expansion, cytokine production, and maintenance of cytotoxic activity, without alteration of CTL phenotype. Furthermore, HA-1-specific polyclonal CTL lines were enriched as efficiently by aAPCs as by autologous HA-1 peptide-pulsed dendritic cells. Thus, aAPCs coated with HLA/mHag complexes, CD80, and CD54 may serve as tools for in vitro enrichment of immunotherapeutic mHag-specific CTL lines.

Antigen Presentation↗

PubMed2004

Phase I trial of large multivalent immunogen derived from melanoma lysates in patients with disseminated melanoma.

PURPOSE: The purpose of this research was to determine the toxicity and immunological activity of large multivalent immunogen (LMI), a preparation of tumor cell membranes affixed to amorphous silica microbeads, in patients with melanoma. EXPERIMENTAL DESIGN: Nineteen patients with metastatic (stage IV) melanoma were entered into the study, of whom 15 received the full 3 months of treatment with LMI. LMI was administered without adjuvant, one-half intradermally (i.d.) and the other half s.c. Because we expected little toxicity, we first treated 2 patients at each dose level, 10-, 30-, or 100-million tumor cell equivalents on weeks 0, 4, and 8, and subsequently randomized the remaining 13 patients to receive treatment with one of those dosage schedules, for a total of 19 patients. Two patients who were registered were found to be ineligible because of brain metastases, and 2 others did not complete the course of treatment for reasons other than toxicity. Thus, 15 patients were fully evaluable. Patients with evidence of a clinical response (at least stable disease at the 12-week checkpoint) had the option of continuing treatment at 4-week intervals. Frequencies of cytolytic T cell precursors against HLA-A2 matched melanoma cells, and delayed-type hypersensitivity to a melanoma cell membrane preparation from a component melanoma cell line were performed to measure immunological efficacy, and serum chemistries and complete blood counts were performed every 2 weeks throughout the study to measure possible toxicity. Computed tomography scans were performed pretreatment and at week 12 to measure possible beneficial effects on known lesions. RESULTS: Eight of the 15 evaluable patients had an increase in cytolytic T-cell precursors during the course of therapy, usually by day 42. No patient had demonstrable delayed-type hypersensitivity to a melanoma membrane preparation before or after treatment. No toxicity of any kind was observed. A degree of clinical effectiveness of LMI was suggested by the elicitation of stable disease in 5 patients at 12 weeks. One patient had >50% regression of a lung nodule but progression of disease to the brain, whereas a second patient had a bona fide partial remission of a 3-cm diameter solitary lung nodule. CONCLUSIONS: LMI was nontoxic, improved immunological reactivity to melanoma cells, and showed evidence of clinical effectiveness (shrinkage of tumor) in 1 patient. Additional studies with LMI with added adjuvant materials, in melanoma and other cancers, appear warranted.

Adjuvants, Immunologic↗

PubMed2003

CD8 T cell clonal expansion and development of effector function require prolonged exposure to antigen, costimulation, and signal 3 cytokine.

Full activation of naive CD8 T cells requires Ag, costimulation, and a third signal that can be provided by IL-12. Brief exposure (6 h) to Ag and B7-1 is sufficient to stimulate multiple rounds of cell division, but clonal expansion and development of effector function are minimal even when signal 3 is present. Full activation instead requires concerted signaling by Ag, B7-1, and IL-12 for greater than 40 h. Thus, the gene expression program required for cell division can be initiated by brief interaction with Ag and costimulation, but maintaining the expression of the genes needed for survival and effector function requires prolonged signaling by a signal 3 cytokine in concert with Ag and costimulation.

Adoptive Transfer↗

PubMed2003

Signal 3 determines tolerance versus full activation of naive CD8 T cells: dissociating proliferation and development of effector function.

Activation of naive CD8 T cells to undergo clonal expansion and develop effector function requires three signals: (a) Ag, (b) costimulation, and (c) IL-12 or adjuvant. The requirement for the third signal to stimulate Ag-dependent proliferation is variable, making the greatest contribution when Ag levels are low. At high Ag levels, extensive proliferation can occur in vitro or in vivo in the absence of a third signal. However, despite having undergone the same number of divisions, cells that expand in the absence of a third signal fail to develop cytolytic effector function. Thus, proliferation and development of cytolytic function can be fully uncoupled. Furthermore, these cells are rendered functionally tolerant in vivo, in that subsequent restimulation with a potent stimulus results in limited clonal expansion, impaired IFN-gamma production, and no cytolytic function. Thus, the presence or absence of the third signal appears to be a critical variable in determining whether stimulation by Ag results in tolerance versus development of effector function and establishment of a responsive memory population.

Animals↗

PubMed2003

In vivo augmentation of tumor-specific CTL responses by class I/peptide antigen complexes on microspheres (large multivalent immunogen).

Tumor membrane Ag immobilized on cell size microspheres (large multivalent immunogen (LMI)) was previously shown to augment tumor-specific CTL activity and reduce tumor growth, and a clinical trial examining this approach is in progress. In the current study, LMI treatment has been examined using adoptive transfer of TCR-transgenic CD8 T cells to visualize Ag-specific cells during the response. OT-I T cells specific for H-2K(b)/OVA(257-264) were transferred into mice that were then challenged with LMI made by immobilizing H-2K(b)/OVA(257-264) on microspheres (K(b)/OVA(257-264)-LMI) alone, or along with i.p. challenge with OVA-expressing E.G7 tumor. K(b)/OVA(257-264)-LMI caused significant reduction of tumor growth when administered to E.G7-bearing mice. When administered alone, the K(b)/OVA(257-264)-LMI caused only weak clonal expansion of OT-I cells in the spleen and lymph nodes, although most of the OT-I cells up-regulated expression of CD44 and VLA-4. In contrast, K(b)/OVA(257-264)-LMI administration to E.G7-bearing mice stimulated no detectable expansion of OT-I cells in the spleen and lymph nodes but caused a rapid increase in the number of OT-I cells in the peritoneal cavity, the site of the growing tumor. These results demonstrate the potential for using class I/tumor peptide complexes for immunotherapy. In addition, they suggest a model for the mechanism of CTL augmentation in which recognition of the LMI Ag results in altered trafficking of the tumor-specific CD8 T cells so that they reach the site of a growing tumor more rapidly and in greater numbers, where they may further expand and acquire effector function.

Adjuvants, Immunologic↗

PubMed2002

The adjuvant effects of Mycobacterium tuberculosis heat shock protein 70 result from the rapid and prolonged activation of antigen-specific CD8+ T cells in vivo.

Heat shock protein 70 (hsp70) is a potent adjuvant that links innate and adaptive immune responses. To study how hsp70 activates naive CD8(+) T cells in vivo, we tracked Ag-specific CD8(+) T cells in mice immunized with a fusion protein containing chicken OVA linked to hsp70 derived from Mycobacterium tuberculosis (OVA.TBhsp70). On a molar basis, OVA.TBhsp70 was several hundred times more effective than OVA peptide plus CFA in eliciting specific CD8(+) T cell responses. Immunization with OVA.TBhsp70 activated >90% of detectable OVA-specific CD8(+) T cells within 3 days and led to the persistence of cytotoxic effectors for at least 17 days. These studies demonstrate that the potent adjuvant effect of M. tuberculosis hsp70 results from the relatively complete, rapid, and durable activation of Ag-specific CD8(+) T cells.

Adjuvants, Immunologic↗

PubMed2002

Opposing effects of IL-2 in tumor immunotherapy: promoting CD8 T cell growth and inducing apoptosis.

Tumors often induce specific CTL responses, but these are usually ineffective at eliminating the growing tumor. The T cell growth factor IL-2 has potential for expanding and prolonging CTL responses, and there is considerable interest in using this cytokine in combination with other immunotherapeutic agents that target T cell responses. Using adoptive transfer of OT-I CD8 T cells specific for OVA(257-264) peptide, and E.G7 tumor cells transfected with OVA, we have examined the effects of IL-2 on the generation and maintenance of a CTL response to the tumor. Administration of IL-2 during the initial phase of the response, clonal expansion, and development of effector function, had no effect on the number of CTL generated or the control of tumor growth. In contrast, a short 2-day time course of low-dose IL-2 at the peak of clonal expansion or at later times resulted in prolonged and expanded responses by the OT-I CTL, with concomitant decrease in tumor load and extension of survival. However, when IL-2 administration was more prolonged, as is often the case in clinical trials, the therapeutic benefit was lost due to elimination of the tumor-specific CTL, at least in part through induction of apoptosis. These results demonstrate that use of IL-2 for tumor immunotherapy is very much a double-edged sword and strongly suggest that more limited time and dose regimens may substantially improve its clinical efficacy when it is used in conjunction with approaches that target CTL responses.

Animals↗

PubMed2002

The poststimulation program of CD4 versus CD8 T cells (death versus activation-induced nonresponsiveness).

Both CD8 and CD4 T cells undergo autocrine IL-2-induced proliferation and clonal expansion following stimulation with Ag and costimulation. The CD8 T cell response is transient because the cells rapidly become activation-induced nonresponsive (AINR) and exhibit split anergy. In these cells, the capacity for IL-2 production is lost, but TCR-mediated IFN-gamma production and cytotoxicity are maintained. At this point, the CTL become dependent on IL-2 provided by CD4 Th cells for continued expansion. If IL-2 is available to support expansion for a brief period, AINR is reversed and the cells regain the ability to produce IL-2. In this study, we show that CD4 T cells do not become AINR, but instead are rendered susceptible to Fas-mediated activation-induced cell death following stimulation through TCR and CD28. Using z-VAD-fmk or anti-Fas ligand mAb to inhibit cell death, we demonstrate that previously activated CD4 T cells retain the ability to up-regulate c-Jun N-terminal kinase activity and IL-2 mRNA levels upon TCR engagement and no longer require costimulation. This rewiring of signaling pathways is similar to that seen following reversal of AINR in CD8 T cells. Thus, CD8 and CD4 T cells appear to use distinct mechanisms, AINR and activation-induced cell death, respectively, to limit excessive clonal expansion following a productive response, while permitting important effector functions to be expressed.

Amino Acid Chloromethyl Ketones↗

PubMed2002

Peptide antigen priming of naive, but not memory, CD8 T cells requires a third signal that can be provided by IL-12.

Challenge with peptide Ag in the absence of adjuvant results in tolerance of CD8 T cells specific for the Ag. In contrast, administration of IL-12 along with peptide results in massive clonal expansion, development of effector function, and establishment of a long-lived memory population. Using adoptive transfer of TCR-transgenic CD8 T cells, this effect of IL-12 is shown to be independent of CD4 T cells and to require costimulation provided by CD28 and possibly LFA-1. IL-12 supports responses when IL-12Rbeta1-deficient mice are used as recipients for the adoptively transferred CD8 T cells, demonstrating that the IL-12 is acting directly on the T cells rather than on host APC. These results provide strong support for a three-signal model for in vivo activation of naive CD8 T cells by peptide Ag, in which the presence or absence of the third signal determines whether tolerance or activation occurs. In contrast, memory CD8 T cells are effectively activated by peptide Ag in the absence of IL-12 or adjuvant.

Abatacept↗

PubMed2002

Activation-induced nonresponsiveness: a Th-dependent regulatory checkpoint in the CTL response.

CD8 T cells undergo autocrine IL-2-dependent proliferation upon TCR engagement and costimulation, but within 3-4 days, they become activation-induced nonresponsive (AINR) and display a split anergy. They can lyse targets and secrete IFN-gamma but they cannot produce IL-2 in response to TCR ligation and costimulation, due at least in part to an inability to up-regulate mitogen-activated protein kinases and IL-2 mRNA. Exogenous IL-2 can drive continued proliferation of AINR cells and nonresponsiveness is reversed within 1-2 days so that Ag-driven proliferation can resume. Mitogen-activated protein kinases and IL-2 mRNA can again be up-regulated, but "rewiring" has occurred so that these events no longer depend upon costimulation; TCR engagement is sufficient. Development of AINR appears to be a normal part of the differentiation program of CD8 T cells, providing a regulatory checkpoint to convert the initial helper-independent response to one that depends upon CD4 T cell help for continued expansion of the effector CTL. Once permission is given, in the form of IL-2, to pass this checkpoint, the CTL can make a prolonged response to persisting Ag in the absence of further CD4 T cell help.

Adjuvants, Immunologic↗