Dual IL-6 and CTLA-4 blockade regresses pancreatic tumors in a T cell and CXCR3-dependent manner

This study aimed to enhance anti-tumor immune responses to pancreatic cancer via antibody-based blockade of IL-6 and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4). Mice bearing subcutaneous or orthotopic pancreatic tumors were treated with blocking antibodies to IL 6 and/or CTLA-4. In both tumor models, dual IL-6 and CTLA-4 blockade significantly inhibited tumor growth. Additional investigations revealed that dual therapy induced an overwhelming infiltration of T cells into the tumor as well as changes in CD4+ T cell subsets. Dual blockade therapy elicited CD4+ T cells to secrete increased IFN-γ in vitro. Likewise, in vitro stimulation of pancreatic tumor cells with IFN-γ profoundly increased tumor cell production of CXCR3 specific chemokines, even in the presence of IL-6. In vivo blockade of CXCR3 prevented orthotopic tumor regression in the presence of the combination treatment, demonstrating a dependence on the CXCR3 axis for anti-tumor efficacy. Both CD4+ and CD8+ T cells were required for the anti-tumor activity of this combination therapy, as their in vivo depletion via antibodies impaired outcomes. These data represent the first report of IL-6 and CTLA 4 blockade as a means to regress pancreatic tumors with defined operative mechanisms of efficacy. Given these results, this therapeutic combination has potential for immediate clinical translation.

Identification of human CD4+ T cell populations with distinct antitumor activity

How naturally arising human CD4+ T helper subsets affect cancer immunotherapy is unclear. We reported that human CD4+CD26high T cells elicit potent immunity against solid tumors. As CD26high T cells are often categorized as TH17 cells for their IL-17 production and high CD26 expression, we posited these populations would have similar molecular properties. Here, we reveal that CD26high T cells are epigenetically and transcriptionally distinct from TH17 cells. Of clinical importance, CD26high and TH17 cells engineered with a chimeric antigen receptor (CAR) regressed large human tumors to a greater extent than enriched TH1 or TH2 cells. Only human CD26high T cells mediated curative responses, even when redirected with a suboptimal CAR and without aid by CD8+ CAR T cells. CD26high T cells cosecreted effector cytokines, produced cytotoxic molecules, and persisted long term. Collectively, our work underscores the promise of CD4+ T cell populations to improve durability of solid tumor therapies.

IL6 Fuels Durable Memory for Th17 Cell-Mediated Responses to Tumors

The accessibility of adoptive T-cell transfer therapies (ACT) is hindered by the cost and time required for product development. Here we describe a streamlined ACT protocol using Th17 cells expanded only 4 days ex vivo. While shortening expansion compromised cell yield, this method licensed Th17 cells to eradicate large tumors to a greater extent than cells expanded longer term. Day 4 Th17 cells engrafted, induced release of multiple cytokines including IL6, IL17, MCP-1, and GM-CSF in the tumor-bearing host, and persisted as memory cells. IL6 was a critical component for efficacy of these therapies via its promotion of long-term immunity and resistance to tumor relapse. Mechanistically, IL6 diminished engraftment of FoxP3⁺ donor T cells, corresponding with robust tumor infiltration by donor effector over regulatory cells for the Day 4 Th17 cell product relative to cell products expanded longer durations ex vivo. Collectively, this work describes a method to rapidly generate therapeutic T-cell products for ACT and implicates IL6 in promoting durable immunity of Th17 cells against large, established solid tumors. SIGNIFICANCE: An abbreviated, 4-day ex vivo expansion method licenses Th17 cells to confer long-lived immunity against solid malignancies via induction of systemic IL6 in the host.See related commentary by Fiering and Ho, p. 3795.

Genomics meets immunity in pancreatic cancer: Current research and future directions for pancreatic adenocarcinoma immunotherapy

Pancreatic adenocarcinoma (PDAC) remains a formidable disease that needs improved therapeutic strategies. Even though immunotherapy has revolutionized treatment for various solid tumor types, it remains largely ineffective in treating individuals with PDAC. This review describes how the application of genome-wide analysis is revitalizing the field of PDAC immunotherapy. Major themes include new insights into the body’s immune response to the cancer, and key immunosuppressive elements that blunt that antitumor immunity. In particular, new evidence indicates that T cell-based antitumor immunity against PDAC is more common, and more easily generated, than previously thought. However, equally common are an array of cellular and molecular defenses employed by the tumor against those T cells. These discoveries have changed how current immunotherapies are deployed and have directed development of novel strategies to better treat this disease. Thus, the impact of genomic analysis has been two-fold: both in demonstrating the heterogeneity of immune targets and defenses in this disease, as well as providing a powerful tool for designing and identifying personalized therapies that exploit each tumor’s unique phenotype. Such personalized treatment combinations may be the key to developing successful immunotherapies for pancreatic adenocarcinoma.

Human CD26high T cells elicit tumor immunity against multiple malignancies via enhanced migration and persistence

CD8⁺ T lymphocytes mediate potent immune responses against tumor, but the role of human CD4⁺ T cell subsets in cancer immunotherapy remains ill-defined. Herein, we exhibit that CD26 identifies three T helper subsets with distinct immunological properties in both healthy individuals and cancer patients. Although CD26^neg T cells possess a regulatory phenotype, CD26^int T cells are mainly naive and CD26^high T cells appear terminally differentiated and exhausted. Paradoxically, CD26^high T cells persist in and regress multiple solid tumors following adoptive cell transfer. Further analysis revealed that CD26^high cells have a rich chemokine receptor profile (including CCR2 and CCR5), profound cytotoxicity (Granzyme B and CD107A), resistance to apoptosis (c-KIT and Bcl2), and enhanced stemness (β-catenin and Lef1). These properties license CD26^high T cells with a natural capacity to traffic to, regress and survive in solid tumors. Collectively, these findings identify CD4⁺ T cell subsets with properties critical for improving cancer immunotherapy.

The role of human CD4⁺ T cell subsets in cancer immunotherapy is still unclear. Here, the authors show that CD26 identifies three CD4⁺ T cell subsets with distinct immunological properties in both healthy individuals and cancer patients.

PI3Kδ Inhibition Enhances the Antitumor Fitness of Adoptively Transferred CD8+ T Cells

Phosphatidylinositol-3-kinase p110δ (PI3Kδ) inhibition by Idelalisib (CAL-101) in hematological malignancies directly induces apoptosis in cancer cells and disrupts immunological tolerance by depleting regulatory T cells. Yet, little is known about the direct impact of PI3Kδ blockade on effector T cells from CAL-101 therapy. Herein, we demonstrate a direct effect of p110δ inactivation via CAL-101 on murine and human CD8⁺ T cells that promotes a strong undifferentiated phenotype (elevated CD62L/CCR7, CD127, and Tcf7). These CAL-101 T cells also persisted longer after transfer into tumor bearing mice in both the murine syngeneic and human xenograft mouse models. The less differentiated phenotype and improved engraftment of CAL-101 T cells resulted in stronger antitumor immunity compared to traditionally expanded CD8⁺ T cells in both tumor models. Thus, this report describes a novel direct enhancement of CD8⁺ T cells by a p110δ inhibitor that leads to markedly improved tumor regression. This finding has significant implications to improve outcomes from next generation cancer immunotherapies.

The Basics of Artificial Antigen Presenting Cells in T Cell-Based Cancer Immunotherapies

Adoptive T cell transfer (ACT) can mediate objective responses in patients with advanced malignancies. There have been major advances in this field, including the optimization of the ex vivo generation of tumor-reactive lymphocytes to ample numbers for effective ACT therapy via the use of natural and artificial antigen presenting cells (APCs). Herein we review the basic properties of APCs and how they have been manufactured through the years to augment vaccine and T cell-based cancer therapies. We then discuss how these novel APCs impact the function and memory properties of T cells. Finally, we propose new ways to synthesize aAPCs to augment the therapeutic effectiveness of antitumor T cells for ACT therapy.

β-catenin and PI3Kδ inhibition expands precursor Th17 cells with heightened stemness and antitumor activity

ICOS costimulation generates Th17 cells with durable memory responses to tumor. Herein, we found that ICOS induces PI3K/p110δ/Akt and Wnt/β-catenin pathways in Th17 cells. Coinhibiting PI3Kδ and β-catenin altered the biological fate of Th17 cells. Th17 cells inhibited of both pathways expressed less RORγt, which, in turn, reduced their ability to secrete IL-17. Unexpectedly, these cells were more effective (than uninhibited cells) at regressing tumor when infused into mice, leading to long-term curative responses. PI3Kδ inhibition expanded precursor Th17 cells with a central memory phenotype that expressed nominal regulatory properties (low FoxP3), while β-catenin inhibition enhanced Th17 multifunctionality in vivo. Remarkably, upon TCR restimulation, RORγt and IL-17 rebounded in Th17 cells treated with PI3Kδ and β-catenin inhibitors. Moreover, these cells regained β-catenin, Tcf7, and Akt expression, licensing them to secrete heightened IL-2, persist, and eradicate solid tumors without help from endogenous NK and CD8 T cells. This finding shines a light on ways to repurpose FDA-approved drugs to augment T cell-based cancer immunotherapies.

Resident memory T cells in the skin mediate durable immunity to melanoma

Tissue-resident memory T (T_RM) cells have been widely characterized in infectious disease settings; however, their role in mediating immunity to cancer remains unknown. We report that skin-resident memory T cell responses to melanoma are generated naturally as a result of autoimmune vitiligo. Melanoma antigen-specific T_RM cells resided predominantly in melanocyte-depleted hair follicles and were maintained without recirculation or replenishment from the lymphoid compartment. These cells expressed CD103, CD69, and CLA (cutaneous lymphocyte antigen), but lacked PD-1 (programmed cell death protein-1) or LAG-3 (lymphocyte activation gene-3), and were capable of making IFN-γ (interferon-γ). CD103 expression on CD8 T cells was required for the establishment of T_RM cells in the skin but was dispensable for vitiligo development. CD103⁺ CD8 T_RM cells were critical for protection against melanoma rechallenge. This work establishes that CD103-dependent T_RM cells play a key role in perpetuating antitumor immunity.

Murine Th17 cells utilize IL-2 receptor gamma chain cytokines but are resistant to cytokine withdrawal-induced apoptosis

Adoptive cellular therapy (ACT) with the Th17 subset of CD4⁺ T cells can cure established melanoma in preclinical models and holds promise for treating human cancer. However, little is known about the growth factors necessary for optimal engraftment and anti-tumor activity of Th17 cells. Due to the central role of IL-2 receptor gamma chain (IL2Rγ-chain) cytokines (IL-2, IL-7, and IL-15) in the activity and persistence of many T cell subsets after adoptive transfer, we hypothesized that these cytokines are important for Th17 cells. We found that Th17 cells proliferated in response to IL-2, IL-7, and IL-15 in vitro. However, in contrast to many other T cell subsets, including conventionally activated CD8⁺ T cells, we found that Th17 cells were resistant to apoptosis in the absence of IL2Rγ-chain cytokines. To determine whether Th17 cells utilize IL2Rγ-chain cytokines in vivo, we tracked Th17 cell engraftment after adoptive transfer with or without cytokine depletion. Depletion of IL-7 and/or IL-2 decreased initial engraftment, while depletion of IL-15 did not. Supplementation of IL-2 increased initial Th17 engraftment. To assess the clinical relevance of these findings, we treated melanoma-bearing mice with Th17 cell adoptive transfer and concurrent cytokine depletion or supplementation. We found that simultaneous depletion of IL-2 and IL-7 decreased therapeutic efficacy, depletion of IL-15 had no effect, and IL-2 supplementation increased therapeutic efficacy. Our results show that Th17 cells are responsive to IL2Rγ-chain cytokines, and provide insight into the application of these cytokines for Th17-based therapeutic strategies.

Th17 cells are refractory to senescence and retain robust antitumor activity after long-term ex vivo expansion

Adoptive immunotherapy for solid tumors relies on infusing large numbers of T cells to mediate successful antitumor responses in patients. While long-term rapid-expansion protocols (REPs) produce sufficient numbers of CD8⁺ T cells for treatment, they also cause decline in the cell's therapeutic fitness. In contrast, we discovered that IL-17-producing CD4⁺ T cells (Th17 cells) do not require REPs to expand 5,000-fold over 3 weeks. Also, unlike Th1 cells, Th17 cells do not exhibit hallmarks of senescence or apoptosis, retaining robust antitumor efficacy in vivo. Three-week-expanded Th17 cells eliminated melanoma as effectively as Th17 cells expanded for 1 week when infused in equal numbers into mice. However, treating mice with large recalcitrant tumors required the infusion of all cells generated after 2 or 3 weeks of expansion, while the cell yield obtained after 1-week expansion was insufficient. Long-term-expanded Th17 cells also protected mice from tumor rechallenge including lung metastasis. Importantly, 2-week-expanded human chimeric antigen receptor-positive (CAR⁺) Th17 cells also retained their ability to regress human mesothelioma, while CAR⁺ Th1 cells did not. Our results indicate that tumor-reactive Th17 cells are an effective cell therapy for cancer, remaining uncompromised when expanded for a long duration owing to their resistance to senescence.

Low signal strength enhances the antitumor activity of human CAR Th17 cells

We reported the antitumor activity of human Th17 cells (engineered to express a chimeric antigen receptor (CAR) that recognizes mesothelin) regresses large human mesothelioma tumors when infused into mice, but it remains unknown what type and what level of co-signal strength impacts their functional fate and antitumor activity. To address this question, human Th17 cells were activated with a high (3 beads: 1 T cell), medium (1:10) or low (1:100) signal via CD3-beads coated with either CD28 or ICOS agonists. We discovered Th17 cells activated with low ICOS signal were highly multifunctional (IL-17A, IFN-γ, IL-2 and IL-22) and possessed a less differentiated phenotype (high CD62L and CD45RA expression) than cells activated with a high ICOS signal. In comparison to low ICOS signal strength, Th17 cells activated with low CD28 signal strength were poorly functional and terminally differentiated. Of clinical significance, in two distinct tumor models (human mesothelioma and murine melanoma), we found that Th17 cells regressed large tumors to a better extent when primed with a low or medium ICOS signal strength compared to if they were activated with a high ICOS signal strength, or with any level of CD28 signal strength. Our data is compelling given that most ACT clinical trials use high CD3/CD28 activation to expand patients’ cells. Specifically, our work suggests the use of a low bead to T cell ratio will result in a more simple and clinically feasible method to expand highly therapeutic T cells for the clinic.

Th17 cells retain antitumor efficacy after long-term ex vivo expansion

Immunotherapies have produced impressive responses in melanoma patients by re-training their immune system to fight their cancer. One of the most successful of these methods is adoptive T cell therapy (ACT), which enriches, expands, and educates a patient’s tumor-reactive T cells before returning them to the patient. This therapy depends on infusing large numbers of cells (upwards of 1010 cells/patient) to mediate tumor regression, while also requiring cells of durable quality capable of sustaining long-term remission. Unfortunately, CD8+ T cells which are most often used, lose their antitumor efficacy as they are expanded ex vivo to large numbers. To circumvent this dilemma, we propose the use of IL-17 producing CD4+ T cells (Th17 cells), for ACT. We found that similar to CD8+ T cells, treatment with Th17 cells was more effective with higher numbers. These numbers can be achieved as Th17 cells expanded up to 10,000 fold after three weeks of ex vivo culture. At the end of culture, Th17 cells were as effective at eradicating melanomas as Th17 cells cultured for shorter duration. Between early and late culture time points, Th17 cells retained an effector memory phenotype (CD44+CD62L−) without acquiring markers of full effector and exhausted status, converted to a Th1-like functional profile (from mainly secreting IL17 to co-secreting IFNγ and IL17), and maintained the ability to engraft and persist in the host. We also demonstrate the power of combining the high yield and durable potency of Th17 cells by using their total yield at late culture to control clinically significant end-stage disease. These results support the advancement of Th17 cells to clinical trials to increase the number, quality, and duration of patient responses to treatment.

Toll-like receptor agonist therapy augments the antitumor activity of adoptively transferred CD8+ T cells without host preconditioning

Lymphodepletion enhances adoptive T cell transfer (ACT) therapy by activating the innate immune system via microbes released from the radiation-injured gut. Microbial LPS is a key mediator of lymphodepletion enhancement, but our ability to use these TLR agonists to bolster the potency of T cell-based cancer therapies remains elusive. Herein, we used LPS as a tool to address how and when to use TLR agonists to improve cancer immunotherapy. We utilized the pmel-1 melanoma mouse model. B16F10-bearing mice were lymphodepleted with 5Gy total body irradiation (TBI) and given a tripartite ACT therapy (consisting of transferred pmel-1 CD8+ T cells, vaccination with fowlpox encoding gp100, and IL-2) along with TLR4 agonist LPS. The timing of LPS administration and the requirement of individual components of the tripartite therapy were evaluated. We discovered that while exogenous administration of LPS was able to enhance CD8+ T cells’ tumor destruction, LPS treatment alone did not replace individual components of the tripartite regimen. Interestingly, administering LPS one day before ACT compromised tumor regression. Conversely, administering LPS after ACT potentiated the antitumor effectiveness of the regimen, thereby supporting the expansion of transferred CD8+ T cells over host Treg cells. Non-toxic TLR agonists MPL and CpG also improved ACT therapy. Finally, TBI preconditioning was no longer needed to regress tumors in mice depleted of host CD4+ T cells, given a tripartite ACT regimen and then treated with a TLR agonist. Collectively, our results identify how and when to administer TLR agonists to augment ACT in the absence of host preconditioning. These findings have implications for the design of next generation T cell therapies.

Toll-like receptor agonist therapy can profoundly augment the antitumor activity of adoptively transferred CD8(+) T cells without host preconditioning

Background

Lymphodepletion enhances adoptive T cell transfer (ACT) therapy by activating the innate immune system via microbes released from the radiation-injured gut. Microbial components, such as LPS, are key mediators of total body irradiation (TBI) enhancement, but our ability to strategically use these toll-like receptor (TLR) agonists to bolster the potency of T cell-based therapies for cancer remains elusive. Herein, we used TLR4 agonist LPS as a tool to address how and when to use TLR agonists to effectively improve cancer immunotherapy.

Methods

To determine the mechanisms of how innate immune activation via lymphodepletion potentiated antitumor T cell immunity, we utilized the pmel-1 melanoma mouse model. B16F10-bearing mice were preconditioned with 5Gy TBI and given a tripartite ACT therapy (consisting of transferred pmel-1 CD8⁺ T cells, vaccination with fowlpox encoding gp100, and IL-2) along with TLR4 agonist LPS. The timing of LPS administration and the requirement of individual components of the tripartite therapy were evaluated based on tumor growth and the phenotype of recovered splenocytes by flow cytometry. We also evaluated the role of non-toxic and clinically used TLR4 and TLR9 agonists—monophosphoryl lipid A (MPL) and CpG Oligodeoxynucleotide (CpG ODN), respectively— for ACT therapy.

Results

Here we report that while exogenous administration of LPS was able to enhance adoptively transferred CD8⁺ T cells’ tumor destruction, LPS treatment alone did not replace individual components of the tripartite ACT regimen, or obviate TBI. Moreover, we found that sequentially administering LPS during or one day prior to ACT therapy compromised tumor regression. In contrast, administering LPS after ACT potentiated the antitumor effectiveness of the regimen, thereby supporting the expansion of transferred tumor-specific CD8⁺ T cells over host CD4⁺ T cells. We also found that non-toxic TLR agonists MPL and CpG potentiated the antitumor activity of infused CD8⁺ T cells. Finally, TBI was no longer needed to regress tumors in mice who were depleted of host CD4⁺ T cells, given a tripartite ACT regimen and then treated with low dose LPS.

Conclusions

Collectively, our results identify how and when to administer TLR agonists to augment T cell-based immunotherapy in the absence or presence of host preconditioning for treatment of advanced malignancies. Our findings have clinical implications for the design of next generation immune-based therapies for patients with cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/s40425-016-0110-8) contains supplementary material, which is available to authorized users.

Dendritic Cells in Irradiated Mice Trigger the Functional Plasticity and Antitumor Activity of Adoptively Transferred Tc17 Cells via IL12 Signaling

PURPOSE

The adoptive cell transfer (ACT) of CD8(+) T cells is a promising treatment for advanced malignancies. Lymphodepletion before ACT enhances IFNγ(+)CD8(+) T cell (Tc0)-mediated tumor regression. Yet, how lymphodepletion regulates the function and antitumor activity of IL17A(+)CD8(+) T cells (Tc17) is unknown.

EXPERIMENTAL DESIGN

To address this question, pmel-1 CD8(+) T cells were polarized to secrete either IL17A or IFNγ. These subsets were then infused into mice with B16F10 melanoma that were lymphoreplete [no total body irradiation (TBI)], or lymphodepleted with nonmyeloablative (5 Gy) or myeloablative (9 Gy with hematopoietic stem cell transplantation) TBI. The activation of innate immune cells and function of donor T-cell subsets were monitored in recipient mice.

RESULTS

Tc17 cells regress melanoma in myeloablated mice to a greater extent than in lymphoreplete or nonmyeloablated mice. TBI induced functional plasticity in Tc17 cells, causing conversion from IL17A to IFNγ producers. Additional investigation revealed that Tc17 plasticity and antitumor activity were mediated by IL12 secreted by irradiated host dendritic cells (DC). Neutralization of endogenous IL12 reduced the antitumor activity of Tc17 cells in myeloablated mice, whereas ex vivo priming with IL12 enhanced their capacity to regress melanoma in nonmyeloablated animals. This, coupled with exogenous administration of low-dose IL12, obviated the need for host preconditioning, creating curative responses in nonirradiated mice.

CONCLUSIONS

Our findings indicate that TBI-induced IL12 augments Tc17 cell-mediated tumor immunity and underline the substantial implications of in vitro preparation of antitumor Tc17 cells with IL12 in the design of T-cell immunotherapies.

The inducible costimulator augments Tc17 cell responses to self and tumor tissue

The inducible costimulator (ICOS) plays a key role in the development of Th17 cells, but its role in the development and antitumor activity of IL-17-producing CD8(+) T cells (Tc17) remains unknown. We found that ICOS costimulation was important for the functional maintenance, but not differentiation, of Tc17 cells in vitro. Blocking the ICOS pathway using an antagonist mAb or by using recipient mice genetically deficient in the ICOS ligand reduced the antitumor activity of adoptively transferred Tc17 cells. Conversely, activating Tc17 cells with an ICOS agonist in vitro enhanced their capacity to eradicate melanoma and induce autoimmune vitiligo when infused into mice. However, ICOS stimulation did not augment the antitumor activity of IL-2 expanded T cells. Additional investigation revealed that ICOS stimulation not only increased IL-2Rα, CXCR3, and IL-23R expression on Tc17 cells, but also dampened their expression of suppressive molecule CD39. Although Tc17 cells activated with an ICOS agonist cosecreted heightened IL-17A, IL-9, and IFN-γ, their therapeutic effectiveness was critically dependent on IFN-γ production. Depletion of IL-17A and IL-9 had little impact on antitumor Tc17 cells activated with an ICOS agonist. Collectively, our work reveals that the ICOS pathway potentiates the antitumor activity of adoptively transferred Tc17 cells. This work has major implications for the design of vaccine, Ab and cell-based therapies for autoimmunity, infectious disease, and cancer.

Orthography plays a critical role in cognate priming: evidence from French/English and Arabic/French cognates

A series of three experiments was carried out in order to better characterize the representations that support long-term cognate priming. In Experiment 1, robust priming was obtained between orthographically similar French/English cognates in bilingual speakers, and this priming was mediated, in part, by orthographic codes, given that priming for these items was dramatically reduced following a study-test modality shift. In Experiment 2, no priming was obtained between the same set of French/English cognates in monolingual English speakers. Finally, in Experiment 3, priming for orthographically unrelated Arabic/French cognates was no larger than cross-modal priming, suggesting that these effects were mediated by nonorthographic representations. The role of orthography in supporting cognate priming is discussed.

The modality-specific and -nonspecific components of long-term priming are frequency sensitive

Five experiments were carried out to test the claim that the modality-specific and modality-nonspecific components of long-term priming are differentially sensitive to word frequency, with the specific component being less affected. In contrast with this claim, specific and nonspecific priming were similarly reduced for high-frequency words in three lexical decision and two perceptual identification experiments. These findings highlight the important role of frequency in modulating priming as well as provide a basic constraint for future theories of priming. In addition, the roles of task and student population in modulating priming are examined.

In defense of abstractionist theories of repetition priming and word identification

There is a great deal of interest in characterizing the representations and processes that support visual word priming and written word identification more generally. On one view, these phenomena are supported by abstract orthographic representations that map together visually dissimilar exemplars of letters and words (e.g., the letters A/a map onto a common abstract letter code a*). On a second view, orthographic codes consist in a collection of episodic representations of words that interact in such a way that it sometimes looks as if there are abstract codes. Tenpenny (1995) contrasted these general approaches and concluded by endorsing the episodic account, arguing that no evidence demands that we posit abstract orthographic representations. This review reconsiders the evidence and argues that a variety of priming and nonpriming research strongly supports the conclusion that abstract orthographic codes exist and support priming and word identification. On this account, episodic representations are represented separately from abstract orthographic knowledge and contribute minimally to these functions.

Orthographic, phonological, and articulatory contributions to masked letter and word priming

A series of experiments assessed masked priming for letters and words that are visually similar (SIM) and dissimilar (DIS) in upper- and lowercase formats. For letters, robust DIS priming was obtained in a naming task, but this priming did not extend to a variety of non-naming tasks. For words, robust DIS priming was obtained in both naming and non-naming tasks. SIM letter and word priming extended to all tasks, but the effects were generally small for letters. The restricted set of conditions for DIS letter priming suggests that this priming is mediated by phonological-articulatory processes, and the generality of DIS word priming argues that abstract orthographic codes mediate these effects. Consistent with this conclusion, priming between homophones (for both letters and words) was found in a naming task, but little word homophone priming was obtained in a lexical decision task.

The potential role of spinal cord cyclooxygenase-2 in the development of Freund's complete adjuvant-induced changes in hyperalgesia and allodynia

Chronic inflammatory conditions produce a state of hyperalgesia which is evident from a few hours to days after administration of an inflammatory stimulus. The molecular mechanisms involved in the initiation of hyperalgesia are not well understood and in this study we have investigated the role of prostaglandins in this process in the rat. Unilateral intraplantar injection of Freund's complete adjuvant produces an immediate localized swelling (oedema) with the development of altered pain responses in the ipsilateral paw such as a reduced threshold to noxious stimuli (hyperalgesia) and lowered thresholds such that normally innocuous stimuli produce a pain response (allodynia). We have monitored levels of cyclooxygenase messenger RNA and prostaglandins in lumbar spinal cord in parallel with these behavioural responses (oedema, hyperalgesia and allodynia) and identified a marked increase in cyclooxygenase-2 messenger RNA (3-fold), maximal at 2-4 h after Freund's complete adjuvant, followed by a significant increase in 6-keto prostaglandin F1alpha and prostaglandin E2 which is maximal by 8 h. Pretreatment of animals with the unselective cyclooxygenase inhibitor indomethacin attenuated oedema (approximately 40%) and allodynia (80-100%), but had no effect on the development of mechanical hyperalgesia. Pretreatment with the cyclooxygenase-2 selective inhibitors DuP 697, flosulide and SC58125 also attenuated allodynia (by 80-100%) but had no effect on the development of oedema or mechanical hyperalgesia. The marked increase in cyclooxygenase-2 messenger RNA in the lumbar spinal cord following intraplantar Freund's complete adjuvant suggests that the cyclooxygenase enzyme and its product may have a role in the adaptive response that occurs in the lumbar spinal cord during a peripheral inflammatory reaction. Pharmacological analysis reveals that prostaglandins are directly involved in the development of allodynia. However, these studies show that the development of mechanical hyperalgesia does not require the production of prostaglandins indicating that more than one pathway mediates the altered pain responses associated with a peripheral inflammatory lesion.

Different perceptual codes support priming for words and pseudowords: was Morton right all along?

A perceptual-identification task was used to assess priming for words and pseudowords that in their upper- and lowercase formats share either few (high-shift items) or many (low-shift items) visual features. Equivalent priming was obtained for high-shift words repeated in the same case and in a different case, and this priming was greatly reduced when there was a study-test modality shift. Accordingly, the cross-case priming was mediated in large part by modality-specific perceptual codes. By contrast, priming for high-shift pseudowords was greatly reduced following the case manipulation, as was so for high-shift words when they were randomly intermixed with pseudowords. Low-shift items were not affected by the case manipulation. On the basis of the overall pattern of results, the author argues that different mechanisms mediate priming for words and pseudowords and that J. Morton (1979) was essentially correct in his characterization of word priming.

Different perceptual codes support priming for words and pseudowords: was Morton right all along?

A perceptual-identification task was used to assess priming for words and pseudowords that in their upper- and lowercase formats share either few (high-shift items) or many (low-shift items) visual features. Equivalent priming was obtained for high-shift words repeated in the same case and in a different case, and this priming was greatly reduced when there was a study-test modality shift. Accordingly, the cross-case priming was mediated in large part by modality-specific perceptual codes. By contrast, priming for high-shift pseudowords was greatly reduced following the case manipulation, as was so for high-shift words when they were randomly intermixed with pseudowords. Low-shift items were not affected by the case manipulation. On the basis of the overall pattern of results, the author argues that different mechanisms mediate priming for words and pseudowords and that J. Morton (1979) was essentially correct in his characterization of word priming.

Does implicit memory extend to legal and illegal nonwords?

In 4 experiments, implicit and explicit memory for words and nonwords were compared. In Experiments 1-2 memory for words and legal nonwords (e.g., kers) was assessed with an identification (implicit) and a recognition (explicit) memory task: Robust priming was obtained for both words and nonwords, and the priming effects dissociated from explicit memory following a levels-of-processing manipulation (Experiment 1) and following a study-test modality shift (Experiment 2). In Experiment 3, priming for legal and illegal nonwords (e.g., xyks) was observed on an identification task, and the effects dissociated from explicit memory following a levels-of-processing manipulation. Finally, in Experiment 4, significant inhibitory priming for legal nonwords was observed when a lexical-decision task was used. Results suggest that implicit memory can extend to legal and illegal nonwords. Implications for theories of implicit memory are discussed.

Implicit memory and test awareness

In three experiments we examined whether normal subjects can perform an implicit test without becoming aware that the test items were previously encountered in the study phase of the experiment. Experiment 1 assessed single word priming with the stem completion task, and subjects who reported awareness/unawareness that the test items were previously encoded in the study task showed equivalent priming. Experiments 2a-c and 3 assessed associative priming with the stem completion task, and in this case, only subjects who were aware that the test items were previously encountered showed associative priming effects. These findings suggest that single word priming and associative priming reflect different memory processes because the former and not the latter effect can be observed in unaware subjects.

Implicit memory and test awareness

In three experiments we examined whether normal subjects can perform an implicit test without becoming aware that the test items were previously encountered in the study phase of the experiment. Experiment 1 assessed single word priming with the stem completion task, and subjects who reported awareness/unawareness that the test items were previously encoded in the study task showed equivalent priming. Experiments 2a-c and 3 assessed associative priming with the stem completion task, and in this case, only subjects who were aware that the test items were previously encountered showed associative priming effects. These findings suggest that single word priming and associative priming reflect different memory processes because the former and not the latter effect can be observed in unaware subjects.