CD4+ T Cell Help Confers a Cytotoxic T Cell Effector Program Including Coinhibitory Receptor Downregulation and Increased Tissue Invasiveness.

CD4+ T cells optimize the cytotoxic T cell (CTL) response in magnitude and quality, by unknown molecular mechanisms. We here present the transcriptomic changes in CTLs resulting from CD4+ T cell help after anti-cancer vaccination or virus infection. The gene expression signatures revealed that CD4+ T cell help during priming optimized CTLs in expression of cytotoxic effector molecules and many other functions that ensured efficacy of CTLs throughout their life cycle. Key features included downregulation of PD-1 and other coinhibitory receptors that impede CTL activity, and increased motility and migration capacities. "Helped" CTLs acquired chemokine receptors that helped them reach their tumor target tissue and metalloprotease activity that enabled them to invade into tumor tissue. A very large part of the "help" program was instilled in CD8+ T cells via CD27 costimulation. The help program thus enhances specific CTL effector functions in response to vaccination or a virus infection.

High-Dimensional Mass Cytometry Reveals Emphysema-associated Changes in the Pulmonary Immune System.

Rationale: Chronic inflammation plays an important role in alveolar tissue damage in emphysema, but the underlying immune alterations and cellular interactions are incompletely understood. Objectives: To explore disease-specific pulmonary immune cell alterations and cellular interactions in emphysema. Methods: We used single-cell mass cytometry (CyTOF) to compare the immune compartment in alveolar tissue from 15 patients with severe emphysema and 5 control subjects. Imaging mass cytometry (IMC) was applied to identify altered cell-cell interactions in alveolar tissue from patients with emphysema (n = 12) compared with control subjects (n = 8). Measurements and Main Results: We observed higher percentages of central memory CD4 T cells in combination with lower proportions of effector memory CD4 T cells in emphysema. In addition, proportions of cytotoxic central memory CD8 T cells and CD127+CD27+CD69- T cells were higher in emphysema, the latter potentially reflecting an influx of circulating lymphocytes into the lungs. Central memory CD8 T cells, isolated from alveolar tissue from patients with emphysema, exhibited an IFN-γ response upon anti-CD3 and anti-CD28 activation. Proportions of CD1c+ dendritic cells, expressing migratory and costimulatory markers, were higher in emphysema. Importantly, IMC enabled us to visualize increased spatial colocalization of CD1c+ dendritic cells and CD8 T cells in emphysema in situ. Conclusions: Using CyTOF, we characterized the alterations of the immune cell signature in alveolar tissue from patients with chronic obstructive pulmonary disease stage III or IV emphysema versus control lung tissue. These data contribute to a better understanding of the pathogenesis of emphysema and highlight the feasibility of interrogating the immune cell signature using CyTOF and IMC in human lung tissue. Clinical trial registered with www.clinicaltrials.gov (NCT04918706).

Effect of combined exposure to phthalates and polycyclic aromatic hydrocarbons during early pregnancy on gestational age and neonatal size: A prospective cohort study.

Many studies have indicated that individual exposure to phthalates (PAEs) or polycyclic aromatic hydrocarbons (PAHs) affects pregnancy outcomes. However, combined exposure to PAEs and PAHs presents a more realistic situation, and research on the combined effects of PAEs and PAHs on gestational age and newborn size is still limited. This study aimed to assess the effects of combined exposure to PAEs and PAHs on neonatal gestational age and birth size. Levels of 9 PAE and 10 PAH metabolites were measured from the urine samples of 1030 women during early pregnancy from the Zunyi Birth Cohort in China. Various statistical models, including linear regression, restricted cubic spline, Bayesian kernel machine regression, and quantile g-computation, were used to study the individual effects, dose-response relationships, and combined effects, respectively. The results of this prospective study revealed that each ten-fold increase in the concentration of monoethyl phthalate (MEP), 2-hydroxynaphthalene (2-OHNap), 2-hydroxyphenanthrene (2-OHPhe), and 1-hydroxypyrene (1-OHPyr) decreased gestational age by 1.033 days (95 % CI: -1.748, -0.319), 0.647 days (95 % CI: -1.076, -0.219), 0.845 days (95 % CI: -1.430, -0.260), and 0.888 days (95 % CI: -1.398, -0.378), respectively. Moreover, when the concentrations of MEP, 2-OHNap, 2-OHPhe, and 1-OHPyr exceeded 0.528, 0.039, 0.012, and 0.002 µg/g Cr, respectively, gestational age decreased in a dose-response manner. Upon analyzing the selected PAE and PAH metabolites as a mixture, we found that they were significantly negatively associated with gestational age, birth weight, and the ponderal index, with 1-OHPyr being the most important contributor. These findings highlight the adverse effects of single and combined exposure to PAEs and PAHs on gestational age. Therefore, future longitudinal cohort studies with larger sample sizes should be conducted across different geographic regions and ethnic groups to confirm the impact of combined exposure to PAEs and PAHs on birth outcomes.

A novel technique for NO.253 lymph node dissection and left colic artery preservation to avoid potential postoperative internal hernia in laparoscopic radical resection for rectal cancer.

BACKGROUND: The preservation of the left colic artery (LCA) has emerged as a preferred approach in laparoscopic radical resection for rectal cancer. However, preserving the LCA while simultaneously dissecting the NO.253 lymph node can create a mesenteric defect between the inferior mesenteric artery (IMA), the LCA, and the inferior mesenteric vein (IMV). This defect could act as a potential "hernia ring," increasing the risk of developing an internal hernia after surgery. The objective of this study was to introduce a novel technique designed to mitigate the risk of internal hernia by filling mesenteric defects with autologous tissue. METHODS: This new technique was performed on eighteen patients with rectal cancer between January 2022 and June 2022. First of all, dissected the lymphatic fatty tissue on the main trunk of IMA from its origin until the LCA and sigmoid artery (SA) or superior rectal artery (SRA) were exposed and then NO.253 lymph node was dissected between the IMA, LCA and IMV. Next, the SRA or SRA and IMV were sequentially ligated and cut off at an appropriate location away from the "hernia ring" to preserve the connective tissue between the "hernia ring" and retroperitoneum. Finally, after mobilization of distal sigmoid, on the lateral side of IMV, the descending colon was mobilized cephalad. Patients'preoperative baseline characteristics and intraoperative, postoperative complications were examined. RESULTS: All patients' potential "hernia rings" were closed successfully with our new technique. The median operative time was 195 min, and the median intraoperative blood loss was 55 ml (interquartile range 30-90). The total harvested lymph nodes was 13.0(range12-19). The median times to first flatus and liquid diet intake were both 3.0 days. The median number of postoperative hospital days was 8.0 days. One patient had an injury to marginal arterial arch, and after mobolization of splenic region, tension-free anastomosis was achieved. No other severe postoperative complications such as abdominal infection, anastomotic leakage, or bleeding were observed. CONCLUSIONS: This technique is both safe and effective for filling the mesenteric defect, potentially reducing the risk of internal hernia following laparoscopic NO.253 lymph node dissection and preservation of the left colic artery in rectal cancer surgeries.

Identification of CMTM6 and CMTM4 as PD-L1 protein regulators.

The clinical benefit for patients with diverse types of metastatic cancers that has been observed upon blockade of the interaction between PD-1 and PD-L1 has highlighted the importance of this inhibitory axis in the suppression of tumour-specific T-cell responses. Notwithstanding the key role of PD-L1 expression by cells within the tumour micro-environment, our understanding of the regulation of the PD-L1 protein is limited. Here we identify, using a haploid genetic screen, CMTM6, a type-3 transmembrane protein of previously unknown function, as a regulator of the PD-L1 protein. Interference with CMTM6 expression results in impaired PD-L1 protein expression in all human tumour cell types tested and in primary human dendritic cells. Furthermore, through both a haploid genetic modifier screen in CMTM6-deficient cells and genetic complementation experiments, we demonstrate that this function is shared by its closest family member, CMTM4, but not by any of the other CMTM members tested. Notably, CMTM6 increases the PD-L1 protein pool without affecting PD-L1 (also known as CD274) transcription levels. Rather, we demonstrate that CMTM6 is present at the cell surface, associates with the PD-L1 protein, reduces its ubiquitination and increases PD-L1 protein half-life. Consistent with its role in PD-L1 protein regulation, CMTM6 enhances the ability of PD-L1-expressing tumour cells to inhibit T cells. Collectively, our data reveal that PD-L1 relies on CMTM6/4 to efficiently carry out its inhibitory function, and suggest potential new avenues to block this pathway.

Bone marrow-derived myeloid progenitors as driver mutation carriers in high- and low-risk Langerhans cell histiocytosis.

Langerhans cell histiocytosis (LCH) is a myeloid neoplasia, driven by sporadic activating mutations in the MAPK pathway. The misguided myeloid dendritic cell (DC) model proposes that high-risk, multisystem, risk-organ-positive (MS-RO+) LCH results from driver mutation in a bone marrow (BM)-resident multipotent hematopoietic progenitor, while low-risk, MS-RO- and single-system LCH would result from driver mutation in a circulating or tissue-resident, DC-committed precursor. We have examined the CD34+c-Kit+Flt3+ myeloid progenitor population as potential mutation carrier in all LCH disease manifestations. This population contains oligopotent progenitors of monocytes (Mo's)/macrophages (MΦs), osteoclasts (OCs), and DCs. CD34+c-Kit+Flt3+ cells from BM of MS-RO+ LCH patients produced Langerhans cell (LC)-like cells in vitro. Both LC-like and DC offspring from this progenitor carried the BRAF mutation, confirming their common origin. In both high- and low-risk LCH patients, CD34+c-Kit+Flt3+ progenitor frequency in blood was higher than in healthy donors. In one MS-RO+ LCH patient, CD34+c-Kit+Flt3+ cell frequency in blood and its BRAF-mutated offspring reported response to chemotherapy. CD34+c-Kit+Flt3+ progenitors from blood of both high- and low-risk LCH patients gave rise to DCs and LC-like cells in vitro, but the driver mutation was not easily detectable, likely due to low frequency of mutated progenitors. Mutant BRAF alleles were found in Mo's /MΦs, DCs, LC-like cells, and/or OC-like cells in lesions and/or Mo and DCs in blood of multiple low-risk patients. We therefore hypothesize that in both high- and low-risk LCH, the driver mutation is present in a BM-resident myeloid progenitor that can be mobilized to the blood.

The CD27 and CD70 costimulatory pathway inhibits effector function of T helper 17 cells and attenuates associated autoimmunity.

T helper 17 (Th17) cells protect against infection but also promote inflammation and autoimmunity. Therefore, the factors that govern Th17 cell differentiation are of special interest. The CD27 and CD70 costimulatory pathway impeded Th17 effector cell differentiation and associated autoimmunity in a mouse model of multiple sclerosis. CD27 or CD70 deficiency exacerbated disease, whereas constitutive CD27 signaling strongly reduced disease incidence and severity. CD27 signaling did not impact master regulators of T helper cell lineage commitment but selectively repressed transcription of the key effector molecules interleukin-17 (IL-17) and the chemokine receptor CCR6 in differentiating Th17 cells. CD27 mediated this repression at least in part via the c-Jun N-terminal kinase (JNK) pathway that restrained IL-17 and CCR6 expression in differentiating Th17 cells. CD27 signaling also resulted in epigenetic silencing of the Il17a gene. Thus, CD27 costimulation via JNK signaling, transcriptional, and epigenetic effects suppresses Th17 effector cell function and associated pathological consequences.

A Novel Technique With Ileal Mesentery to Reconstruct the Pelvic Peritoneum After Pelvic Dissection With End Colostomy for Rectal Cancer.

BACKGROUND: After abdominoperineal resection, low anterior resection, and end colostomy for lower rectal cancer, it is necessary to reconstruct the pelvic peritoneum to avoid small bowel obstruction, perineal hernia, and radiation enteritis in patients for whom postoperative radiotherapy is planned. However, pelvic peritoneal closure is technically difficult in patients who lack enough peritoneum to cover the defect or have received neoadjuvant radiation and have a rigid pelvis. IMPACT OF INNOVATION: The impact of this innovation is to reconstruct the pelvic peritoneum with the distal ileal mesentery laparoscopically. TECHNOLOGY, MATERIALS AND METHODS: After removal of the tumor, the distal ileal mesentery was selected to completely cover the defect. Subsequently, suturing of the ileal mesentery to the posterior wall of the urinary bladder and all sides of the pelvic cavity was performed. Finally, the patients were returned to the headfirst supine position to ensure that there was no small bowel falling into the pelvic dead space. PRELIMINARY RESULTS: All surgical procedures were successfully performed laparoscopically from January 2019 to April 2021. No perineal complications or intestinal obstructions occurred during the follow-up period. CONCLUSIONS AND FUTURE DIRECTIONS: This novel technique was found to be safe and effective. Moreover, it provided an economical method for the reconstruction of the pelvic peritoneum using autologous material, which could preserve the small intestine in the abdomen to avoid related complications. Additional larger series of patients with longer follow-up are needed to validate the safety and feasibility of this method.

Radiomics-based signature of breast cancer on preoperative contrast-enhanced MRI to predict axillary metastasis.

Aim: This study aimed to predict axillary metastasis using radiology features in dynamic contrast-enhanced MRI. Methods: This study included 243 breast lesions confirmed as malignant based on axillary status. Most outcome-predictive features were selected using four machine-learning algorithms. Receiver operating characteristic analysis was used to reflect diagnostic performance. Results: Least absolute shrinkage and selection operator was used to dimensionally reduce 1137 radiomics features to three features. Three optimal radiomics features were used to model construction. The logistic regression model achieved an accuracy of 97% and 85% in the training and test groups. Clinical utility was evaluated using decision curve analysis. Conclusion: The novel combination of radiomics analysis and machine-learning algorithm could predict axillary metastasis and prevent invasive manipulation.

Clinically applicable CD34+-derived blood dendritic cell subsets exhibit key subset-specific features and potently boost anti-tumor T and NK cell responses.

Allogeneic stem cell transplantation (alloSCT), following induction chemotherapy, can be curative for hemato-oncology patients due to powerful graft-versus-tumor immunity. However, disease recurrence remains the major cause of treatment failure, emphasizing the need for potent adjuvant immunotherapy. In this regard, dendritic cell (DC) vaccination is highly attractive, as DCs are the key orchestrators of innate and adaptive immunity. Natural DC subsets are postulated to be more powerful compared with monocyte-derived DCs, due to their unique functional properties and cross-talk capacity. Yet, obtaining sufficient numbers of natural DCs, particularly type 1 conventional DCs (cDC1s), is challenging due to low frequencies in human blood. We developed a clinically applicable culture protocol using donor-derived G-CSF mobilized CD34+ hematopoietic progenitor cells (HPCs) for simultaneous generation of high numbers of cDC1s, cDC2s and plasmacytoid DCs (pDCs). Transcriptomic analyses demonstrated that these ex vivo-generated DCs highly resemble their in vivo blood counterparts. In more detail, we demonstrated that the CD141+CLEG9A+ cDC1 subset exhibited key features of in vivo cDC1s, reflected by high expression of co-stimulatory molecules and release of IL-12p70 and TNF-α. Furthermore, cDC1s efficiently primed alloreactive T cells, potently cross-presented long-peptides and boosted expansion of minor histocompatibility antigen-experienced T cells. Moreover, they strongly enhanced NK cell activation, degranulation and anti-leukemic reactivity. Together, we developed a robust culture protocol to generate highly functional blood DC subsets for in vivo application as tailored adjuvant immunotherapy to boost innate and adaptive anti-tumor immunity in alloSCT patients.

A New Medial-to-Lateral Approach for Laparoscopic D3 Lymphadenectomy plus Complete Mesocolic Excision (D3 + CME) for Right-Sided Colon Cancer.

BACKGROUND: D3 lymphadenectomy is important for accurate staging and provides long-term benefits, especially for T3-4/N + tumors.1,2 Both D3 lymphadenectomy as well as complete mesocolic excision (CME) require central ligation of vessels at their origins to ensure radical resection.3 Currently, superior mesentery vein (SMV) is navigated by ileocolic vessels while its sheath is dissected stepwise from caudal to cranial.4-6 This report describes a new medial-to-lateral approach for laparoscopic right hemicolectomy with D3 + CME. METHODS: The patient was a 47-year-old man with diagnosis of hepatic flexure cancer (cT4N1M0). First, the pedicle of the middle colic vessels and ileocolic vessels were both grasped, then the sheath of SMV was dissected at its left side as there are fewer blood vessels entering here compared with its right side. Second, after identification of middle colic artery (MCA), SMV was skeletonized from medial to lateral and no. 213 and no. 203 lymph nodes were dissected. Third, MCA and ileocolic vein and artery (ICV and ICA) were ligated at their roots. After separating the transverse mesocolon from the duodenum, the branches of the Henle trunk were exposed and no. 223 lymph nodes were dissected. Accessory right colic vein, right colic vein, and middle colic vein were ligated respectively. Fourth, the ascending mesocolon was separated from the retroperitoneal tissues through the front side of Toldt's fascia, the mesocolon was mobilized completely, and the tumor was removed en bloc. RESULTS: The operation time was 175 min, with estimated blood loss of 50 ml. The patient recovered well without bleeding complications and was discharged on postoperative day 7. Histology revealed moderately differentiated adenocarcinoma with 5 of 24 lymph nodes involved (pT3N2M0). CONCLUSIONS: The medial-to-lateral approach presented in the video might be helpful for standardization of laparoscopic D3 + CME for right-sided colon cancer.

People living with HIV easily lose their immune response to SARS-CoV-2: result from a cohort of COVID-19 cases in Wuhan, China.

BACKGROUND: To date, whether the immune response for SARS-CoV-2 infection among people living with HIV(PLWH) is different from HIV-naïve individuals is still not clear. METHODS: In this cohort study, COVID-19 patients admitted to hospitals in Wuhan between January 15 and April 1, 2020, were enrolled. Patients were categorized into PLWH and HIV-naïve group. All patients were followed up regularly (every 15 days) until November 30, 2020, and the immune response towards SARS-CoV-2 was observed. RESULTS: Totally, 18 PLWH and 185 HIV-naïve individuals with COVID-19 were enrolled. The positive conversion rates of IgG were 56% in PLWH and 88% in HIV-naïve patients respectively, and the peak was on the 45th day after COVID-19 onset. However, the positive rate of IgG dropped to 12% in PLWH and 33% among HIV-naïve individuals by the end of the study. The positive conversion rate of IgG among asymptomatic carriers is significantly lower than that among patients with moderate disease (AOR = 0.24, 95% CI 0.07-0.85). PLWH had a lower IgG seroconversion rate (AOR = 0.11, 95% CI 0.03-0.39) and shorter IgG duration (AHR = 3.99, 95% CI 1.43-11.13) compared to HIV-naïve individuals. Patients with higher lymphocyte counts at onset had a lower positive conversion rate (AOR = 0.30, 95% CI 0.10-0.87) and shorter duration for IgG (AHR = 4.01, 95% CI 1.78-9.02). CONCLUSIONS: The positive conversion rate of IgG for SARS-CoV-2 was relatively lower and quickly lost in PLWH.

Ratiometric fluorescence detection of riboflavin based on fluorescence resonance energy transfer from nitrogen and phosphorus co-doped carbon dots to riboflavin.

Fluorescent nitrogen and phosphorus co-doped carbon dots (NPCDs) were prepared via a hydrothermal method with citric acid and O-phosphorylethanolamine as precursors. The overlap between the absorption spectrum of riboflavin and the fluorescence emission spectrum of the NPCDs and the relative proximity of the NPCDs to riboflavin due to hydrogen bonding facilitated the formation of a NPCDs/riboflavin fluorescence resonance energy transfer (FRET) system. Thus, a ratiometric fluorescence method for the detection of riboflavin based on the formation of this NPCDs/riboflavin FRET system was developed. The method displayed a sensitive and selective response to riboflavin in the range 0.5-50 µmol/L with a detection limit of 0.17 µmol/L. It was also found to be suitable for the detection of riboflavin in milk and riboflavin pharmaceutical tablets. Graphical abstract Illustration of the preparation of NPCDs and the ratiometric fluorescence detection of riboflavin using the NPCDs/riboflavin FRET system.

Hydrothermal synthesis of carbon dots codoped with nitrogen and phosphorus as a turn-on fluorescent probe for cadmium(II).

Nitrogen and phosphorus co-doped carbon dots (N,P-CDs) have been synthesized via hydrothermal method starting from o-phosphorylethanolamine and citric acid. The blue-green fluorescence of the N,P-CDs (with excitation/emission peaks at 325/435 nm) is gradually enhanced on sequential addition of Cd(II) ions. This fluorometric assay works in the 0.5 µM to 12.5 µM Cd(II) concentration range and has a 0.16 µM detection limit. The phenomenon may be attributed to chelation enhanced fluorescence that is induced by the formation of Cd(II)-N,P-CDs complex with functional groups present on the surface. The method has applied to the detection of Cd(II) in spiked serum and urine samples and gave satisfying results. Graphical abstract Schematic presentation of the synthesis of nitrogen and phosphorus co-doped carbon dots (N,P-CDs) and their application as a turn-on fluorescence probe for Cd(II) detection.

Hydrothermal synthesis of nitrogen and copper co-doped carbon dots with intrinsic peroxidase-like activity for colorimetric discrimination of phenylenediamine isomers.

Carbon dots doped with nitrogen and copper have been synthesized via a hydrothermal method. They possess favorable peroxidase-like catalytic activity over a wide range of pH values and temperatures. Specifically, they were used to catalyze the oxidation of ortho- and para-phenylenediamine (OPD and PPD) by H2O2. The resulting products possess different colors (yellow for OPD and brown for PPD), which can be visually discriminated. The corresponding typical absorption peaks of oxidized products for OPD and PPD are at 413 nm and 500 nm, respectively. The method displays excellent discrimination ability and selectivity over potential interferents. The detection limits are 1.1 µM for OPD and 1.9 µM for PPD. The respective linear ranges are from 5 to 200 µM for OPD and from 2.5 to 700 µM for PPD. The method was applied to the quantification of OPD and PPD in spiked natural waters. Graphical abstract Schematic presentation of the synthesis of nitrogen and copper co-doped carbon dots (N,Cu-CDs) and their application as an enzyme mimic for colorimetric discrimination of ortho-, meta- and para-phenylenediamine (OPD, MPD and PPD).

Expression of costimulatory ligand CD70 on steady-state dendritic cells breaks CD8+ T cell tolerance and permits effective immunity.

Steady-state dendritic cells (DCs) maintain peripheral T cell tolerance, whereas mature DCs generate immunity. CD70 is a costimulatory ligand acquired upon DC maturation. To determine its impact on T cell fate, we have generated mice that constitutively express CD70 in conventional DCs (cDCs). In these mice, naive CD4+ and CD8+ T cells spontaneously convert into effector cells. Administration of peptide without adjuvant, which is ordinarily tolerogenic, elicited tumor-eradicating CD8+ T cell responses and robust CD4+ T cell-independent memory. CD70 was also constitutively expressed in cDCs that inducibly present viral epitopes. In this case, tolerance induction was prevented as well. The antigen-presenting DCs generated protective immunity to virus infection and broke a pre-existing state of CD8+ T cell tolerance. Thus, the sole expression of CD70 by otherwise immature cDCs sufficed to convert CD8+ T cell tolerance into immunity, defining the importance of CD27-CD70 interactions at the interface between T cell and DC.

Osteoclast precursors in murine bone marrow express CD27 and are impeded in osteoclast development by CD70 on activated immune cells.

Osteoclasts (OCs) are bone-resorbing cells that are formed from hematopoietic precursors. OCs ordinarily maintain bone homeostasis, but they can also cause major pathology in autoimmune and inflammatory diseases. Under homeostatic conditions, receptor activator of nuclear factor kappa-B (RANK) ligand on osteoblasts drives OC differentiation by interaction with its receptor RANK on OC precursors. During chronic immune activation, RANK ligand on activated immune cells likewise drives pathogenic OC differentiation. We here report that the related TNF family member CD70 and its receptor CD27 can also mediate cross-talk between immune cells and OC precursors. We identified CD27 on a rare population (0.3%) of B220(-)c-Kit(+)CD115(+)CD11b(low) cells in the mouse bone marrow (BM) that are highly enriched for osteoclastogenic potential. We dissected this population into CD27(high) common precursors of OC, dendritic cells (DCs) and macrophages and CD27(low/neg) downstream precursors that could differentiate into OC and macrophages, but not DC. In a recombinant mouse model of chronic immune activation, sustained CD27/CD70 interactions caused an accumulation of OC precursors and a reduction in OC activity. These events were due to a CD27/CD70-dependent inhibition of OC differentiation from the OC precursors by BM-infiltrating, CD70(+)-activated immune cells. DC numbers in BM and spleen were increased, suggesting a skewing of the OC precursors toward DC differentiation. The impediment in OC differentiation culminated in a high trabecular bone mass pathology. Mice additionally presented anemia, leukopenia, and splenomegaly. Thus, under conditions of constitutive CD70 expression reflecting chronic immune activation, the CD27/CD70 system inhibits OC differentiation and favors DC differentiation.

CD8+ T cells produce the chemokine CXCL10 in response to CD27/CD70 costimulation to promote generation of the CD8+ effector T cell pool.

Various cell types can produce the chemokine CXCL10 in response to IFN-γ stimulation. CXCL10 is generally viewed as a proinflammatory chemokine that promotes recruitment of CD8÷ and Th1-type CD4÷ effector T cells to infected or inflamed nonlymphoid tissues. We show that CXCL10 plays a role during CD8÷ T cell priming in the mouse. Genome-wide expression profiling revealed the Cxcl10 gene as a target of CD27/CD70 costimulation in newly activated CD8÷ T cells. CD27/CD70 costimulation is known to promote activated T cell survival, but CXCL10 did not affect survival or proliferation of primed CD8÷ T cells in vitro. Accordingly, CXCL10 could not fully rescue CD27 deficiency in mice infected with influenza virus. Rather, CXCL10 acted as chemoattractant for other activated CD8⁺ T cells. It signaled downstream of CD27 in a paracrine fashion to promote generation of the CD8÷ effector T cell pool in the Ag-draining lymph nodes. Consistently, CD8÷ T cells required expression of the CXCL10 receptor CXCR3 for their clonal expansion in a CD27/CD70-dependent peptide-immunization model. Our findings indicate that CXCL10, produced by primed CD8÷ T cells in response to CD27/CD70 costimulation, signals to other primed CD8⁺ T cells in the lymph node microenvironment to facilitate their participation in the CD8÷ effector T cell pool.