Prolonged antigen survival and cytosolic export in cross-presenting human γδ T cells

Human blood Vγ9Vδ2 T cells respond to signals from microbes and tumors and subsequently differentiate into professional antigen-presenting cells (γδ T-APCs) for induction of CD4⁺ and CD8⁺ T cell responses. γδ T-APCs readily take up and degrade exogenous soluble protein for peptide loading on MHC I, in a process termed antigen cross-presentation. The mechanisms underlying antigen cross-presentation are ill-defined, most notably in human dendritic cells (DCs), and no study has addressed this process in γδ T-APCs. Here we show that intracellular protein degradation and endosomal acidification were significantly delayed in γδ T-APCs compared with human monocyte-derived DCs (moDCs). Such conditions are known to favor antigen cross-presentation. In both γδ T-APCs and moDCs, internalized antigen was transported across insulin-regulated aminopeptidase (IRAP)–positive early and late endosomes; however, and in contrast to various human DC subsets, γδ T-APCs efficiently translocated soluble antigen into the cytosol for processing via the cytosolic proteasome-dependent cross-presentation pathway. Of note, γδ T-APCs cross-presented influenza antigen derived from virus-infected cells and from free virus particles. The robust cross-presentation capability appears to be a hallmark of γδ T-APCs and underscores their potential application in cellular immunotherapy.     

Role of T lymphocytes in rat 2,4,6-trinitrobenzene sulphonic acid (TNBS) induced colitis: increased mortality after gammadelta T cell depletion and no effect of alphabeta T cell depletion

BACKGROUND AND AIM: Indirect evidence suggests that CD4+ T cells have a pathogenic while gammadelta T cells have a protective role in the initiation and perpetuation of inflammatory bowel disease. To define the role of T cell subsets in a rat colitis model (2,4,6-trinitrobenzene sulphonic acid (TNBS)) we analysed colitis severity after effective depletion of T helper cells, alphabeta T cells, or gammadelta T cells. METHODS: T helper cells, alphabeta T cells, or gammadelta T cells were depleted using previously described monoclonal antibodies directed at the CD4 molecule (OX38), the CD2 molecule (OX34, both depleting CD4+ T cells), the alphabeta T cell receptor (R73), and the gammadelta T cell receptor (V65). Depletion was verified by flow cytometry and/or immunohistology. Colitis was induced using intracolonic application of TNBS. RESULTS: Surprisingly, depletion of T helper cells or alphabeta T cells had no influence on survival, macroscopic or microscopic scores, or myeloperoxidase activity following colitis induction. In contrast, depletion of gammadelta T cells resulted in significantly increased mortality (V65: 73%, n=15) compared with controls (30%, n=13; p<0.03). In addition, colitis was histologically more severe in the gammadelta T cell depleted group compared with controls (p<0.05). CONCLUSIONS: T helper cells or alphabeta T cells did not influence the initiation or perpetuation of rat TNBS colitis. In contrast, gammadelta T cells had a protective role in rat TNBS colitis as depletion caused increased mortality.     

Identification of a panel of ten cell surface protein antigens associated with immunotargeting of leukemias and lymphomas by peripheral blood �æ� T cells

Background

Vγ9Vδ2 T lymphocytes are regarded as promising mediators of cancer immunotherapy due to their capacity to eliminate multiple experimental tumors, particularly within those of hematopoietic origin. However, Vγ9Vδ2 T-cell based lymphoma clinical trials have suffered from the lack of biomarkers that can be used as prognostic of therapeutic success.

Design and Methods

We have conducted a comprehensive study of gene expression in acute lymphoblastic leukemias and non-Hodgkin’s lymphomas, aimed at identifying markers of susceptibility versus resistance to Vγ9Vδ2 T cell-mediated cytotoxicity. We employed cDNA microarrays and quantitative real-time PCR to screen 20 leukemia and lymphoma cell lines, and 23 primary hematopoietic tumor samples. These data were analyzed using state-of-the-art bioinformatics, and gene expression patterns were correlated with susceptibility to Vγ9Vδ2 T cell mediated cytolysis in vitro.

Results

We identified a panel of 10 genes encoding cell surface proteins that were statistically differentially expressed between “γδ-susceptible” and “γδ-resistant” hematopoietic tumors. Within this panel, 3 genes (ULBP1, TFR2 and IFITM1) were associated with increased susceptibility to Vγ9Vδ2 T-cell cytotoxicity, whereas the other 7 (CLEC2D, NRP2, SELL, PKD2, KCNK12, ITGA6 and SLAMF1) were enriched in resistant tumors. Furthermore, some of these candidates displayed a striking variance of expression among primary follicular lymphomas and T-cell acute lymphoblastic leukemias.

Conclusions

Our results suggest that hematopoietic tumors display a highly variable repertoire of surface proteins that can impact on Vγ9Vδ2 cell-mediated immunotargeting. The prognostic value of the proposed markers can now be evaluated in upcoming Vγ9Vδ2 T cell-based lymphoma/leukemia clinical trials.     

Malignant T gamma/delta lymphoproliferative disease with natural killer lytic activity.

A 17-year-old girl presented with a lymphoproliferative disease involving the bone marrow, peripheral blood, and liver associated with reactive hyperplasia of the spleen. Neoplastic cells were atypical medium-sized lymphoblasts with convoluted nuclei and nucleoli without features of large granular lymphocytes (LGL). The phenotype was CD3+ CD4- CD8-, TCR alpha/beta-, TCR gamma/delta+, delta TCS1-, and CD16+, and these cells exhibited spontaneous natural killer (NK) activity. DNA analysis showed rearrangement of the TCR gamma gene but not of TCR beta or of Ig mu genes. This unusual lymphoproliferative disease may represent the neoplastic expansion of a minor subset of normal T gamma/delta cells with NK activity.     

Overexpression of nuclear β-catenin in rectal adenocarcinoma is associated with radioresistance

AIM:To investigate the association between nuclearβ-catenin overexpression in rectal adenocarcinoma and radioresistance.METHODS:A retrospective analysis was conducted.The analysis involved 136 patients with locally advanced rectal adenocarcinoma who underwent shortcourse preoperative radiotherapy and radical resection.The expression ofβ-catenin in both pretreatment biopsy specimens and resected primary tumor tissues was examined by immunohistochemistry.The correlation ofβ-catenin expression with radioresistance was evaluated using the tumor regression grading(TRG)system.The relationship betweenβ-catenin expression and clinicopathological characteristics was also analyzed.Univariate and logistic multivariate regression analyses were adopted to determine the independent factors of radioresistance.RESULTS:Nuclearβ-catenin overexpression was more evident in radioresistant rectal adenocarcinoma than in radiosensitive rectal adenocarcinoma(57.6%vs 16.7%,P<0.001).Nuclearβ-catenin was overexpressed in favor of poor TRG(≤2),whereas membraneβ-catenin was expressed in favor of good TRG(≥3).Nuclearβ-catenin expression in tumor cell differentiation(P=0.018),lymph node metastasis(P=0.022),and TRG(P<0.001)showed significant differences.Univariate analyses demonstrated that radioresistance is associated with nuclearβ-catenin overexpression(P<0.001).In addition,logistic multivariate regression analysis indicated that only three factors,namely,tumor size(P<0.001),tumor cell differentiation(P<0.001),and nuclearβ-catenin overexpression(P<0.001),are associated with radioresistance.By using radioresistance as a prediction target,nuclearβ-catenin-based prediction alone achieved 83%accuracy,65%sensitivity,and88%specificity.CONCLUSION:Nuclearβ-catenin overexpression may be a valuable candidate to predict the response of rectal adenocarcinoma to preoperative radiotherapy.     

Clinical significance of regulatory T cells in patients with myelodysplastic syndrome

Objective: Foxp3⁺ regulatory T cells (Tregs) play a central role in maintaining immune tolerance. Their expansion in malignant diseases leads to the suppression of host anti‐tumour responses. In this study, we evaluated the clinical significance of Tregs in patients with myelodysplastic syndrome (MDS). Patients and Methods: We analysed the number of CD4⁺ CD25⁺ Foxp3⁺ Tregs using three‐colour flow cytometry in the peripheral blood of 26 patients with MDS classified according to the World Health Organization classification method into four cases of refractory anaemia and refractory anaemia with ringed sideroblasts (RA/RARS), 15 cases of refractory cytopenia with multilineage dysplasia (RCMD), three cases of refractory anaemia with excess blast‐1 (RAEB‐1) and four cases of refractory anaemia with excess blast‐2 (RAEB‐2). Eighteen healthy volunteers were included as the control group. Results: The mean absolute numbers of Tregs in the RA/RARS group (0.06 × 10⁹/L; 95% CI, 0.02–0.10 × 10⁹/L) and RAEB group (0.06 × 10⁹/L; 95% CI, 0.02–0.10 × 10⁹/L) were significantly higher than that of the control group (0.03 × 10⁹/L; 95% CI, 0.02–0.03 × 10⁹/L) (P < 0.05). However, in the RCMD group, there was no significant difference in the mean absolute number of Tregs (0.03 × 10⁹/L; 95% CI, 0.02–0.04 × 10⁹/L) compared with the control group. Regarding the mean level of the CD8/Foxp3 ratio, there were significant decreases in the RA/RARS group (2.8; 95% CI, 0.7–4.9; P < 0.01), RCMD group (3.4; 95% CI, 2.0–4.4; P < 0.001) and RAEB group (2.1; 95% CI, 1.7–2.5; P < 0.001) compared with the control group (6.1; 95% CI, 5.1–7.0). Conclusions: The expansion of natural CD4⁺ Tregs may contribute to the suppression of CD8 through the Th1‐mediated immune response in MDS. The low CD8/Foxp3 ratio is a characteristic feature in MDS. To determine whether the expansion of CD4⁺ Tregs contributes to the progression of MDS subtypes into more aggressive subtypes, more MDS cases and further follow‐up are required.     

Adoptive immunotherapy mediated by ex vivo expanded natural killer T cells against CD1d-expressing lymphoid neoplasms

Background

CD1d is a monomorphic antigen presentation molecule expressed in several hematologic malignancies. Alpha-galactosylceramide (α-GalCer) is a glycolipid that can be presented to cytotoxic CD1d-restricted T cells. These reagents represent a potentially powerful tool for cell mediated immunotherapy.

Design and Methods

We set up an experimental model to evaluate the use of adoptively transferred cytotoxic CD1d-restricted T cells and α-GalCer in the treatment of mice engrafted with CD1d⁺ lymphoid neoplastic cells. To this end the C1R cell line was transfected with CD1c or CD1d molecules. In addition, upon retroviral infection firefly luciferase was expressed on C1R transfected cell lines allowing the evaluation of tumor growth in xenografted immunodeficient NOD/SCID mice.

Results

The C1R-CD1d cell line was highly susceptible to specific CD1d-restricted T cell cytotoxicity in the presence α-GalCer in vitro. After adoptive transfer of CD1d-restricted T cells and α-GalCer to mice engrafted with both C1R-CD1c and C1R-CD1d, a reduction in tumor growth was observed only in CD1d⁺ masses. In addition, CD1d-restricted T-cell treatment plus α-GalCer eradicated small C1R-CD1d⁺ nodules. Immunohistochemical analysis revealed that infiltrating NKT cells were mainly observed in CD1d nodules.

Conclusions

Our results indicate that ex vivo expanded cytotoxic CD1d-restricted T cells and α-GalCer may represent a new immunotherapeutic tool for treatment of CD1d⁺ hematologic malignancies.     

NK T cells provide lipid antigen-specific cognate help for B cells

The mechanisms of T cell help for production of antilipid antibodies are largely unknown. This study shows that invariant NK T cells (iNK T cells) and B cells cooperate in a model of antilipid antigen-specific antibody responses. We use a model haptenated lipid molecule, 4-hydroxy-3-nitrophenyl-alphaGalactosylCeramide (NP-alphaGalCer), to demonstrate that iNK T cells provide cognate help to lipid-antigen-presenting B cells. B cells proliferate and IgG anti-NP is produced from in vivo-immunized mice and in vitro cocultures of B and NK T cells after exposure to NP-alphaGalCer, but not closely related control glycolipids. This B cell response is absent in CD1d(-/-) and Jalpha18(-/-) mice but not CD4(-/-) mice. The antibody response to NP-alphaGalCer is dominated by the IgM, IgG3, and IgG2c isotypes, and marginal zone B cells stimulate better in vitro lipid antigen-driven proliferation than follicular B cells, suggesting an important role for this B cell subset. iNK T cell help for B cells is shown to involve cognate help from CD1d-instructed lipid-specific iNK T cells, with help provided via CD40L, B7-1/B7-2, and IFN-gamma, but not IL-4. This model provides evidence of iNK T cell help for antilipid antibody production, an important aspect of infections, autoimmune diseases, and vaccine development. Our findings also now allow prediction of those microbial antigens that would be expected to elicit cognate iNKT cell help for antibody production, namely those that can stimulate iNKT cells and at the same time have a polar moiety that can be recognized by antibodies.     

Viral PB1-F2 and host IFN-γ guide ILC2 and T cell activity during influenza virus infection

Functional plasticity of innate lymphoid cells (ILCs) and T cells is regulated by host environmental cues, but the influence of pathogen-derived virulence factors has not been described. We now report the interplay between host interferon (IFN)-γ and viral PB1-F2 virulence protein in regulating the functions of ILC2s and T cells that lead to recovery from influenza virus infection of mice. In the absence of IFN-γ, lung ILC2s from mice challenged with the A/California/04/2009 (CA04) H1N1 virus, containing nonfunctional viral PB1-F2, initiated a robust IL-5 response, which also led to improved tissue integrity and increased survival. Conversely, challenge with Puerto Rico/8/1934 (PR8) H1N1 virus expressing fully functional PB1-F2, suppressed IL-5⁺ ILC2 responses, and induced a dominant IL-13⁺ CD8 T cell response, regardless of host IFN-γ expression. IFN-γ–deficient mice had increased survival and improved tissue integrity following challenge with lethal doses of CA04, but not PR8 virus, and increased resistance was dependent on the presence of IFN-γR⁺ ILC2s. Reverse-engineered influenza viruses differing in functional PB1-F2 activity induced ILC2 and T cell phenotypes similar to the PB1-F2 donor strains, demonstrating the potent role of viral PB1-F2 in host resistance. These results show the ability of a pathogen virulence factor together with host IFN-γ to regulate protective pulmonary immunity during influenza infection.

Innate lymphoid cells (ILCs) and T cells represent critical populations of cells that have diverse roles in inflammation and protection (1, 2). Both cell populations consist of subsets that differ in cytokine expression and function. While T cells are important for viral clearance, they can also exacerbate lung immunopathology (1, 3–5) Among ILC subsets, ILC2s play a critical role in pulmonary immunity, particularly in maintaining the lung barrier surface (6–9). During infection, ILC2s respond to the epithelial cell–derived cytokines IL-25, IL-33, and thymic stromal lymphopoietin, and produce the type 2 cytokine IL-5 (10–12). This, in turn, can lead to increased eosinophil recruitment and airway hyperreactivity (AHR) (8, 13–15). Like T cells, ILC2s can play both beneficial and detrimental roles during viral lung infection (6–8).It is known that host cytokines can regulate the activity of ILC and T cell subsets. For example, we previously found that interferon (IFN)-γ deficiency results in enhanced ILC2 activity and increased survival from challenge with the 2009 pandemic strain A/California/04/2009 (CA04) influenza A virus (8). However, our current studies have shown no effect of IFN-γ following challenge with the Puerto Rico/8/1934 (PR8) influenza A virus, a strain that is a commonly used model for the highly virulent 1918 pandemic influenza virus. Although both strains are H1N1 influenza A viruses, they have striking differences in expression of functional PB1-F2, a viral proapoptotic protein that is associated with immunopathology and mortality (16). While the PR8 viral strain expresses full-length PB1-F2, the PB1-F2 gene in the CA04 strain is truncated and nonfunctional (16–20). As a result, the PR8 virus exhibits significantly increased virulence compared to the CA04 viral strain. However, the impact of PB1-F2 on the lymphocyte function that is critical for protection during influenza is not known. A better understanding of the role of pathogen virulence factors in regulating immune cell activity during influenza may aid in designing future therapies for human use.We hypothesized that the PB1-F2 virulence protein can differentially regulate ILC2 and T cell activity in conjunction with host IFN-γ signaling. To test this hypothesis, we have investigated pulmonary immunity in wild-type (WT) and IFN-γ–deficient BALB/c mice infected with PB1-F2 gene reassortant PR8 and CA04 viruses. Our findings demonstrate that viral virulence genes, together with host factors, play critical roles in regulating both ILC2 and T cell responses during influenza, and this, in turn, determines host survival.     

自身免疫性肝炎患者肝内调节性T细胞的数量变化及其意义

目的 研究自身免疫性肝炎(AIH)患者外周血及肝内CD4+ CD25+调节性T细胞（Treg细胞）数量和功能变化.方法 应用流式细胞技术,比较正常人（25例）、慢性乙型肝炎(CHB)患者（18例）和AIH患者（25例）外周血中Treg细胞的变化;应用免疫组织化学染色方法进行Foxp3染色,比较CHB患者（15例）和AI...     

The Unknown Unknowns: Recovering Gamma-Delta T Cells for Control of Human Immunodeficiency Virus (HIV)

Recent advances in γδ T cell biology have focused on the unique attributes of these cells and their role in regulating innate and adaptive immunity, promoting tissue homeostasis, and providing resistance to various disorders. Numerous bacterial and viral pathogens, including human immunodeficiency virus-1 (HIV), greatly alter the composition of γδ T cells in vivo. Despite the effectiveness of antiretroviral therapy (ART) in controlling HIV and restoring health in those affected, γδ T cells are dramatically impacted during HIV infection and fail to reconstitute to normal levels in HIV-infected individuals during ART for reasons that are not clearly understood. Importantly, their role in controlling HIV infection, and the implications of their failure to rebound during ART are also largely unknown and understudied. Here, we review important aspects of human γδ T cell biology, the effector and immunomodulatory properties of these cells, their prevalence and function in HIV, and their immunotherapeutic potential.     

γδT细胞在3型鼠肝炎病毒诱导的小鼠慢性病毒性肝炎中作用的探讨

目的:探讨在3型鼠肝炎病毒(MHV-3)诱导的鼠慢性病毒性肝炎模型中随着感染时间的延长肝脏γδT细胞在肝脏T细胞中的比例变化以及细胞因子IFN(干扰素)-γ的表达.方法:C3H/Hej小鼠腹腔注射10pfu(空斑形成单位)MHV-3建立小鼠慢性病毒性肝炎模型,应用流式细胞技术荧光分析法检测MHV-3感染后0天、5天、10天、15天、20天肝脏中γδT细胞在T细胞中的比例变化及其表达IFN-γ的比例.结果:随着MHV-3感染时间的延长,模型中肝脏γδT细胞在肝脏T细胞中的比例较0天逐渐升高(P＜0.05),在感染后10天达到最高值.肝脏γδT细胞大量表达IFN-γ,在MHV-3感染10天后达到最高值.结论:感染MHV-3后C3H/Hej小鼠体内γδT细胞的数量增加并表达IFN-γ,提示γδT细胞参与了MHV-3诱导的小鼠慢性病毒性肝炎的发生发展过程.     

Mesenteric B cells centrally inhibit CD4+ T cell colitis through interaction with regulatory T cell subsets

Inflammatory bowel disease reflects an aberrant mucosal CD4+ T cell response to commensal enteric bacteria. In addition to regulatory T cell subsets, recent studies have revealed a protective role of B cells in murine CD4+ T cell colitis, but the relationship of their action to T cell immunoregulation is unknown. Here we report that mesenteric lymph node (MLN) B cells protect mice from colitis induced by Galphai2-/- CD4+ T cells. Protection required the transfer of both B cells and CD8alpha+ T cells; neither cell type alone was sufficient to inhibit CD4+ T cell-mediated colitis. Similar results were also observed in colitis induced by CD4+CD45RBhi T cells. Immunoregulation was associated with localization of B cells and expansion of CD4-CD8- CD3+NK1.1+ T cells in the secondary lymphoid compartment, as well as expansion of CD4+CD8alpha+ T cells in the intestinal intraepithelial compartment. MLN B cells from Galphai2-/- mice were deficient in a phenotypic subset and failed to provide cotransfer colitis protection. These findings indicate that protective action of B cells is a selective trait of MLN B cells acquired through a Galphai2-dependent developmental process and link B cells with the formation of regulatory T cells associated with mucosal immune homeostasis.     

Different molecular defects of G gamma (A gamma delta beta)o-thalassaemia in Thailand

DNA from members of 2 Thai families with conditions considered to be delta beta-thalassaemia were studied by using restriction endonuclease DNA mapping. The propositus in family A is a double heterozygote for beta-thalassaemia and delta beta-thalassaemia. DNA analysis reveals a deletion of the beta-globin gene cluster starting at the area between the Sac I and Eco RI sites near the 3' end of the G gamma-gene and extending through the A gamma-, delta- and beta-genes to an unknown extent downstream. In family B, the propositus is delta beta-thalassaemia/Hb E. Deletion of the beta-globin gene cluster begins in the large intervening sequence of the A gamma-gene and removes both delta- and beta-genes downstream.     

Characterization of Adaptive-like γδ T Cells in Ugandan Infants during Primary Cytomegalovirus Infection

Gamma-delta (γδ) T cells are unconventional T cells that help control cytomegalovirus (CMV) infection in adults. γδ T cells develop early in gestation, and a fetal public γδ T cell receptor (TCR) clonotype is detected in congenital CMV infections. However, age-dependent γδ T cell responses to primary CMV infection are not well-understood. Flow cytometry and TCR sequencing was used to comprehensively characterize γδ T cell responses to CMV infection in a cohort of 32 infants followed prospectively from birth. Peripheral blood γδ T cell frequencies increased during infancy, and were higher among CMV-infected infants relative to uninfected. Clustering analyses revealed associations between CMV infection and activation marker expression on adaptive-like Vδ1 and Vδ3, but not innate-like Vγ9Vδ2 γδ T cell subsets. Frequencies of NKG2C⁺CD57⁺ γδ T cells were temporally associated with the quantity of CMV shed in saliva by infants with primary infection. The public γδ TCR clonotype was only detected in CMV-infected infants <120 days old and at lower frequencies than previously described in fetal infections. Our findings support the notion that CMV infection drives age-dependent expansions of specific γδ T cell populations, and provide insight for novel strategies to prevent CMV transmission and disease.     

Nanoparticle-enabled innate immune stimulation activates endogenous tumor-infiltrating T cells with broad antigen specificities

Tumors are often infiltrated by T lymphocytes recognizing either self- or mutated antigens but are generally inactive, although they often show signs of prior clonal expansion. Hypothesizing that this may be due to peripheral tolerance, we formulated nanoparticles containing innate immune stimulants that we found were sufficient to activate self-specific CD8⁺ T cells and injected them into two different mouse tumor models, B16F10 and MC38. These nanoparticles robustly activated and/or expanded antigen-specific CD8⁺ tumor-infiltrating T cells, along with a decrease in regulatory CD4⁺ T cells and an increase in Interleukin-17 producers, resulting in significant tumor growth retardation or elimination and the establishment of immune memory in surviving mice. Furthermore, nanoparticles with modification of stimulating human T cells enabled the robust activation of endogenous T cells in patient-derived tumor organoids. These results indicate that breaking peripheral tolerance without regard to the antigen specificity creates a promising pathway for cancer immunotherapy.

Cancer immunotherapy has held out the promise of harnessing a patient’s own immune system to attack cancer cells for many years. While checkpoint inhibitors and chimeric antigen receptor T cells have triggered long-term remissions in some patients, many more do not respond or have a recurrence, hence the need for additional approaches (1–5). Tumor-infiltrating T cells (TILs), which are found in approximately one-third of the most common tumor types (6, 7), are often either self-antigen or mutated antigen (neoantigen) specific (8, 9), although recent analyses have also documented T cells specific for infectious diseases (10, 11). Self-antigen–specific T cells are particular characteristics of tumor types with lower tumor mutational burden and poorer outcomes (12–14), suggesting that activating these T cells might be particularly beneficial for immunotherapy. Although for many years, it has been thought that almost all self-antigen–specific T cells were deleted in the thymus due to negative selection (15, 16), our own studies of healthy human blood donors (17, 18) and parallel work in mice (19) have shown that only a fraction (∼70 to 0%) of the self-specific T cells is actually eliminated. We also observed profound differences in the activation requirements in the self-antigen–specific vs. foreign antigen-specific T cells—while the latter could be stimulated with cognate antigen plus anti-CD28 and Interleukin (IL)-2, the former could not. Since anti-CD3 could stimulate both cells in vitro, the results suggested that the self-specific T cells were not anergic, but rather, lacked some other signals. Reasoning that these signals were likely related to those triggered by an active infection, as suggested by the classical work of Ohashi and colleagues (20) and others, we surveyed a range of agonists for pattern recognition receptors (PRRs). We found that just two, the lipoprotein (Pam3CysSerLys4 [Pam3CSK4]), an agonist for the Toll-like receptor 1/2 heterodimer (TLR1/2), and muramyl dipeptide (L18-MDP), an agonist for the cytosolic nucleotide-binding oligomerization domain receptor 2 (NOD2), were sufficient to stimulate self-antigen–specific CD8⁺ T cells in vitro as efficiently as foreign antigen-specific CD8⁺ T cells, where both were in the presence of IL-2 and anti-CD28. These results support the hypothesis that self-specific T cells are held in a nonreactive state unless activated by an infection, with its mobilization of the innate immune system.In our previous human colon carcinoma studies (21, 22), both CD4⁺ and CD8⁺ TILs showed extensive clonal expansion, indicating that they had been very active at one point but likely were no longer. Consistent with this aborted response phenomenon is earlier work showing that in metastatic melanoma patients, tumor-associated “self”-antigen–specific CD8⁺ T cells recognizing peptides from melanoma antigen recognized by T cells 1 (MART-1), gp100, and tyrosinase are present in the circulation in much higher frequency than baseline but in an inactive or only partially active state compared with virus-specific T cells in the same patients (12). Also suggesting an arrest in activity are the results of cell transfer experiments, where Yee et al. (23) transferred large numbers of MART-1–specific CD8⁺ T cells in melanoma patients and observed only short-term activity arrested after a few days.Thus, we hypothesized that tumor-infiltrating self-specific and perhaps even neoantigen-specific CD8⁺ T cells could be in a quiescent state similar to that of self-specific T cells in the periphery, and breaking this type of peripheral tolerance might activate these cells and trigger antitumor immunity. However, if given systemically, many of these agents will elicit severe inflammatory toxicities (24, 25). The systemic activation of self-specific CD8⁺ T cells in particular would also likely induce autoimmunity (26). To address these issues, we developed a biodegradable nanoparticle (NP) platform, covalently conjugated with an anti-CD28 antibody (Ab) and capable of delivering IL-2, Pam3CSK4, and L18-MDP in a sustained manner to achieve continuous local stimulation in the tumor microenvironment and minimize the side effects that would likely result from systemic exposure.Using this NP, we first demonstrated that self-specific CD8⁺ T cells isolated from either peripheral blood mononuclear cells (PBMCs) of healthy humans or the tumor-draining lymph nodes of B16F10 melanoma-inoculated mice could be expanded in vitro with NP-enabled stimulation in the presence of relevant self-peptides. Second, we showed that the repeated injection of these NPs into mice bearing either the B16F10 melanoma or MC38 colon carcinoma could generally activate both self-antigen and neoantigen-specific TILs, leading to significant retardation of tumor growth and prolongation of survival in these treated mice. Some mice totally rejected tumors and were completely resistant to tumor reinoculation, indicating that their immune system has acquired systemic “memory.” Evidence suggests that this antitumor activity is, at least in part, due to a reduction in the number and suppressive activity of regulatory T cells (Tregs) and the maturation of antigen-presenting cells (APCs). We further demonstrated that this approach could stimulate human TILs in patient-derived tumor organoids from three different cancer types, even those unresponsive to checkpoint blockades. Altogether, these results indicate that breaking peripheral tolerance with a combination of innate immune stimulants to activate both self-antigen– and neoantigen-specific TILs represents a broadly applicable and effective strategy for cancer immunotherapy.