Detection of SARS-CoV-2-Specific Humoral and Cellular Immunity in COVID-19 Convalescent Individuals.

The World Health Organization has declared SARS-CoV-2 virus outbreak a worldwide pandemic. However, there is very limited understanding on the immune responses, especially adaptive immune responses to SARS-CoV-2 infection. Here, we collected blood from COVID-19 patients who have recently become virus-free, and therefore were discharged, and detected SARS-CoV-2-specific humoral and cellular immunity in eight newly discharged patients. Follow-up analysis on another cohort of six patients 2 weeks post discharge also revealed high titers of immunoglobulin G (IgG) antibodies. In all 14 patients tested, 13 displayed serum-neutralizing activities in a pseudotype entry assay. Notably, there was a strong correlation between neutralization antibody titers and the numbers of virus-specific T cells. Our work provides a basis for further analysis of protective immunity to SARS-CoV-2, and understanding the pathogenesis of COVID-19, especially in the severe cases. It also has implications in developing an effective vaccine to SARS-CoV-2 infection.

Loss to gain: pseudogenes in microorganisms, focusing on eubacteria, and their biological significance.

Pseudogenes are defined as "non-functional" copies of corresponding parent genes. The cognition of pseudogenes continues to be refreshed through accumulating and updating research findings. Previous studies have predominantly focused on mammals, but pseudogenes have received relatively less attention in the field of microbiology. Given the increasing recognition on the importance of pseudogenes, in this review, we focus on several aspects of microorganism pseudogenes, including their classification and characteristics, their generation and fate, their identification, their abundance and distribution, their impact on virulence, their ability to recombine with functional genes, the extent to which some pseudogenes are transcribed and translated, and the relationship between pseudogenes and viruses. By summarizing and organizing the latest research progress, this review will provide a comprehensive perspective and improved understanding on pseudogenes in microorganisms. KEY POINTS: • Concept, classification and characteristics, identification and databases, content, and distribution of microbial pseudogenes are presented. • How pseudogenization contribute to pathogen virulence is highlighted. • Pseudogenes with potential functions in microorganisms are discussed.

Electric-Field-Enhanced Electroluminescence Color Tuning of Colloidal Type-II Tetrapods.

Color-tunable electroluminescence (EL) from a single emitting material can be used to develop single-pixel multicolor displays. However, finding materials capable of broad EL color tuning remains challenging. Herein, we report the observation of broad voltage-tunable EL in colloidal type-II InP/ZnS quantum-dot-seeded CdS tetrapod (TP) LEDs. The EL color can be tuned from red to bluish white by varying the red and blue emission intensities from type-II interfaces and arms, respectively. The capacitor device proves that an external electric field can enhance the color tuning in type-II TPs. COMSOL simulations, numerical calculations, and transient absorption measurements are performed to understand the underlying photophysical mechanism. Our results indicate that the reduced hole relaxation rate from the arm to the quantum dot core can enhance the emission from the CdS arms, which is favorable for EL color tuning. This study provides a novel method to realize voltage-tunable EL colors with potential in display and micro-optoelectronic applications.

Photocatalyzed Direct α-Alkylation of Esters Using Styrenes.

A mild photocatalyzed approach to achieve the α-alkylation of esters via formation of an α -radical is disclosed here. Cesium enolates of esters were generated in situ using Cs2CO3 as a base. A subsequent photocatalyzed oxidation at the α-carbon of these enolates produced an α-radical that was added into activated alkenes. This is the first example accessing the α-carbon radical of esters in photoredox catalyed transformations.

Four Routes to 3-(3-Methoxy-1,3-dioxopropyl)pyrrole, a Core Motif of Rings C and E in Photosynthetic Tetrapyrroles.

The photosynthetic tetrapyrroles share a common structural feature comprised of a ß-ketoester motif embedded in an exocyclic ring (ring E). As part of a total synthesis program aimed at preparing native structures and analogues, 3-(3-methoxy-1,3-dioxopropyl)pyrrole was sought. The pyrrole is a precursor to analogues of ring C and the external framework of ring E. Four routes were developed. Routes 1-3 entail a Pd-mediated coupling process of a 3-iodopyrrole with potassium methyl malonate, whereas route 4 relies on electrophilic substitution of TIPS-pyrrole with methyl malonyl chloride. Together, the four routes afford considerable latitude. A long-term objective is to gain the capacity to create chlorophylls and bacteriochlorophylls and analogues thereof by facile de novo means for diverse studies across the photosynthetic sciences.

Combined Photoredox and Carbene Catalysis for the Synthesis of γ-Aryloxy Ketones.

N-heterocyclic carbenes (NHCs) have emerged as catalysts for the construction of C-C bonds in the synthesis of substituted ketones under single-electron processes. Despite these recent reports, there still remains a need to increase the utility and practicality of these reactions by exploring new radical coupling partners. Herein, we report the synthesis of γ-aryloxyketones via combined NHC/photoredox catalysis. In this reaction, an α-aryloxymethyl radical is generated via oxidation of an aryloxymethyl potassium trifluoroborate salt, which is then added into styrene derivatives to provide a stabilized benzylic radical. Subsequent radical-radical coupling reaction with an azolium radical affords the γ-aryloxy ketone products.

Syntheses and Properties of Metalated Tetradehydrocorrins.

The monoanionic tetrapyrrolic macrocycle B,C-tetradehydrocorrin (TDC) resides chemically between corroles and corrins. This chemical space remains largely unexplored due to a lack of reliable synthetic strategies. We now report the preparation and characterization of Co(II)- and Ni(II)-metalated TDC derivatives ([Co-TDC]+ and [Ni-TDC]+, respectively) with a combination of crystallographic, electrochemical, computational, and spectroscopic techniques. [Ni-TDC]+ was found to undergo primarily ligand-centered electrochemical reduction, leading to hydrogenation of the macrocycle under cathodic electrolysis in the presence of acid. Transient absorption (TA) spectroscopy reveals that [Ni-TDC]+ and the two-electron-reduced [Ni-TDC]- possess long-lived excited states, whereas the excited state of singly reduced [Ni-TDC] exhibits picosecond dynamics. The Co(I) compound [Co-TDC] is air stable, highlighting the notable property of the TDC ligand to stabilize low-valent metal centers in contradistinction to other tetrapyrroles such as corroles, which typically stabilize metals in higher oxidation states.

T Follicular Helper Cells Regulate Humoral Response for Host Protection against Intestinal Citrobacter rodentium Infection.

Citrobacter rodentium colonizes at the colon and causes mucosal inflammation in mice. Previous studies have revealed the importance of the innate and adaptive immune response for controlling C. rodentium infection. In the present study, we examined the role of T follicular helper (Tfh) cells in intestinal C. rodentium infection using mice with Bcl6 deficiency in T cells. Tfh cells were absolutely required at the late, but not the early, phase to control infection. Compared with control mice, we observed systemic pathogen dissemination and more severe colitis in Tfh-deficient mice. Furthermore, the susceptibility of Tfh-deficient mice correlated with an impaired serum IgG1 response to infection, and serum Abs from infected wild-type mice protected Tfh-deficient mice from infection. The transfer of wild-type Tfh cells also restored the levels of IgG1 and led to effective clearance of the pathogens in Tfh-deficient mice. Moreover, during C. rodentium infection, IL-21- and IL-4-producing Tfh cells were increased obviously in wild-type mice, correlating with IgG1 as the major isotype in germinal center B cells. Taken together, our work highlights the requirement and the function of Tfh cells in regulating humoral response for the host protection against C. rodentium infection.

Synthesis of AD-Dihydrodipyrrins Equipped with Latent Substituents of Native Chlorophylls and Bacteriochlorophylls.

Native chlorophylls and bacteriochlorophylls share a common trans-substituted pyrroline ring D (17-propionic acid, 18-methyl), whereas diversity occurs in ring A particularly at the 3-position. Two dihydrodipyrrins equipped with native-like D-ring substituents and tailorable A-ring substituents have been synthesized. The synthesis relies on a Schreiber-modified Nicholas reaction to construct the stereochemically defined precursor to ring D, a dialkyl-substituted pent-4-ynoic acid. The carboxylic acid group of the intact propionic acid proved unworkable, whereupon protected propionate (-CO2tBu) and several latent propyl ethers were examined. The tert-butyldiphenylsilyl-protected propanol substituent proved satisfactory for reaction of the chiral N-acylated oxazolidinone, affording (2S,3S)-2-(3-((tert-butyldiphenylsilyl)oxy)propyl)-3-methylpent-4-ynoic acid in ∼30% yield over 8 steps. Two variants for ring A, 2-tert-butoxycarbonyl-3-Br/H-5-iodo-4-methylpyrrole, were prepared via the Barton-Zard route. Dihydrodipyrrin formation from the pyrrole and pentynoic acid entailed Jacobi Pd-mediated lactone formation, Petasis methenylation, and Paal-Knorr-type pyrroline formation. The two AD-dihydrodipyrrins bear the D-ring methyl and protected propanol groups with a stereochemical configuration identical to that of native (bacterio)chlorophylls, and a bromine or no substitution in ring A corresponding to the 3-position of (bacterio)chlorophylls. The analogous ß-position of a lactone-pyrrole intermediate on the path to the dihydrodipyrrin also was successfully brominated, opening opportunities for late-stage diversification in the synthesis of (bacterio)chlorophylls.

Proximity ligation assay: an ultrasensitive method for protein quantification and its applications in pathogen detection.

It is of great significance to establish sensitive and accurate pathogen detection methods, considering the continuous emergence or re-emergence of infectious diseases seriously influences the safety of human and animals. Proximity ligation assay (PLA) is developed for the sensitive protein detection and also can be used for the detection of pathogens. PLA employs aptamer or monoclonal/polyclonal antibody-nucleic acid complexes as proximity probes. When the paired proximity probes bind to the same target protein or protein complex, they will be adjacent to each other and form an amplifiable DNA sequence through ligation. Combining the specificity of enzyme-linked immunosorbent assay (ELISA) and sensitivity of polymerase chain reaction (PCR), PLA transforms the detection of protein into the detection of DNA nucleic acid sequence. Therefore, as an ultrasensitive protein assay, PLA has great potential for quantification, localization of protein, and clinical diagnostics. In this review, we summarize the basic principles of PLA and its applications in pathogen detection. KEY POINTS: • Different forms of proximity ligation assay are introduced. • Applications of proximity ligation assay in pathogen detection are summarized. • Proximity ligation assay is an ultrasensitive method to quantify protein and pathogen.

Coordinated histone modifications and chromatin reorganization in a single cell revealed by FRET biosensors.

The dramatic reorganization of chromatin during mitosis is perhaps one of the most fundamental of all cell processes. It remains unclear how epigenetic histone modifications, despite their crucial roles in regulating chromatin architectures, are dynamically coordinated with chromatin reorganization in controlling this process. We have developed and characterized biosensors with high sensitivity and specificity based on fluorescence resonance energy transfer (FRET). These biosensors were incorporated into nucleosomes to visualize histone H3 Lys-9 trimethylation (H3K9me3) and histone H3 Ser-10 phosphorylation (H3S10p) simultaneously in the same live cell. We observed an anticorrelated coupling in time between H3K9me3 and H3S10p in a single live cell during mitosis. A transient increase of H3S10p during mitosis is accompanied by a decrease of H3K9me3 that recovers before the restoration of H3S10p upon mitotic exit. We further showed that H3S10p is causatively critical for the decrease of H3K9me3 and the consequent reduction of heterochromatin structure, leading to the subsequent global chromatin reorganization and nuclear envelope dissolution as a cell enters mitosis. These results suggest a tight coupling of H3S10p and H3K9me3 dynamics in the regulation of heterochromatin dissolution before a global chromatin reorganization during mitosis.

[Expression of Ras-Associated Protein 1 in the Vascular Endothelium of Bone Tissue with Non-Traumatic Osteonecrosis of Femoral Head].

Objective: To investigate the difference in the expression of Ras-associated protein 1 (Rap1) in necrotic and healthy areas of non-traumatic osteonecrosis of femoral head (NONFH) patients. Methods: Femoral head tissue samples from 30 cases of NONFH and 30 cases of traumatic osteonecrosis of the femoral head (TONFH) were collected after hip replacement surgery, respectively. No significant difference of Association Research Circulation Osseous (ARCO) staging was found between the NONFH and the TONFH groups ( Z=-0.769, P=0.442). In the NONFH group, 8 patients were ARCO stage IIIb, 10 were stage IV, and 12 were stage V, while in the TONFH ground, 11 patients were ARCO stage IIIb, 9 were stage IV, and 10 were stage V. There were 19 males and 11 females in the NONFH group, with an average age of 49.6 yr. (26-69 yr.), and 16 males and 14 females in the TONFH group, with an average age of 54.2 yr. (37-68 yr.). There was no significant difference in gender or age between the two groups ( P>0.05). Specimens were collected from different bone areas, including those from the necrotic areas (area A) and the healthy areas (area B) of the NONFH group, and those from the healthy areas (area B') of the TONFH group, i.e., the control group. Western blot and quantitative real-time reverse transcription PCR (qRT-PCR) were used to analyze the different expression of Rap1, vascular endothelial growth factor (VEGF) protein, phosphoinositide 3-kinase (PI3K), and Akt protein and their corresponding mRNA in the three areas of bone tissue. HE staining and immunohistochemisty staining were done in order to observe the morphological changes of each area. Results: Western blot results indicated that there was no statistical difference in the relative expression of Rap1, VEGF, PI3K, and Akt proteins ( P>0.05). The relative expressions of Rap1, VEGF, PI3K, and Akt proteins in the area A were lower than those in the area B and the difference was statistically significant ( P<0.05). qRT-PCR results showed that the relative expressions of Rap1, VEGF, PI3 K and Akt mRNA in area A were lower than those of area B, and a statistical difference was found ( P<0.05). The relative expression of the mRNA of Rap1, VEGF , PI3 K and Akt in area B and area B' were not significantly different ( P>0.05). HE staining and immunohistochemisty staining showed that chondrocytes decreased in the necrotic area (area A) of NONFH, chondrocytes nucleus disappeared, subchondral bone trabeculae were broken, bone trabeculae thickened, and empty bone lacunae appeared. Granulation tissues composed of new capillaries and fibrous cells have proliferated and crawled around the necrotic area. Positive expressions of the Rap1, VEGF, PI3K and Akt proteins in area A were weaker than those of the normal area. In addition, there were positive expressions of Rap1, PI3K and Akt on the trabecular bone of both area A and area B at similar intensity of expression. There were strong positive expressions of Rap1, VEGF, PI3K and Akt on the intima of arterioles and venules, and on the peripheral stromal cell membrane, but the positive expression in area A was significantly lower than that in area B. However, the positive expression positions and intensity of all indicators were similar in area B and area B'. Conclusion: The necrosis in NONFH may be related to vascular endothelial damages caused by the inhibition of the Rap1-PI3K/Akt signaling pathways and the subsequent decline in the protein expression.

Use of the Nascent Isocyclic Ring to Anchor Assembly of the Full Skeleton of Model Chlorophylls.

The chlorophyll skeleton contains a chlorin macrocycle and an annulated fifth (or isocyclic) ring bearing 131-oxo and 132-carbomethoxy substituents. The isocyclic ring has traditionally been constructed by annulation of an intact tetrapyrrole macrocycle. Here, a complementary route employs reaction of a gem-dimethyl-substituted dihydrodipyrrin-carboxaldehyde (AD half) and a dipyrromethane bearing a 3-methoxy-1,3-dioxopropyl group (BC half). A McMurry-like reaction of a 2-(2-nitro-5-oxohexyl)pyrrole was employed to construct the second pyrrole ring in one of three BC halves, whereas the other two were prepared by known routes. An AD half and a BC half were joined by Knoevenagel condensation at room temperature, affording the AD,BC-substituted 2-methoxycarbonyl-2-propenone. The subsequent reaction of three AD, BC-propenones (mixture of Z,E-isomers) in CH3CN containing InCl3 and In(OTf)3 at 80 °C afforded the chlorophyll skeleton as the chloroindium(III) chelate; the reaction proceeds via Nazarov cyclization (to form the isocyclic ring), SEAr (to construct the macrocycle), and 2e-,2H+ oxidation (to give the aromatic chromophore). The absorption spectra of the complexes closely resemble that of chlorophyll a. The present work exploits the nascent isocyclic ring as an anchor for directed assembly of the AD and BC halves, forming both the chlorin macrocycle and the isocyclic ring in a single-flask transformation.

Asymmetric Synthesis of a Bacteriochlorophyll Model Compound Containing trans-Dialkyl Substituents in Ring D.

Challenges to the de novo synthesis of bacteriochlorophyll a (BChl a), the chief pigment for anoxygenic bacterial photosynthesis, include creating the macrocycle along with the trans-dialkyl substituents in both pyrroline rings (B and D). A known route to a model bacteriochlorophyll with a gem-dimethyl group in each pyrroline ring has been probed for utility in the synthesis of BChl a by preparation of a hybrid macrocycle (BC-1), which contains a trans-dialkyl group in ring D and a gem-dimethyl group in ring B. Stereochemical definition began with the synthesis of (2S,3S)-2-ethyl-3-methylpent-4-ynoic acid, a precursor to the trans-dialkyl-substituted AD dihydrodipyrrin. Knoevenagel condensation of the latter and a gem-dimethyl, ß-ketoester-substituted BC dihydrodipyrrin afforded the enone (E, 70%; Z, 3%); subsequent double-ring cyclization of the E-enone (via Nazarov, electrophilic aromatic substitution, and elimination reactions) gave BC-1 (53% yield) along with a trace of chlorin byproduct (1.4% relative to BC-1 upon fluorescence assay). BC-1 exhibited the desired trans-dialkyl stereochemistry in ring D and was obtained as a 7:1 mixture of (expected) epimers owing to the configuration of the 132-carbomethoxy substituent. The strategy wherein trans-dialkyl substituents are installed very early and carried through to completion, as validated herein, potentially opens a synthetic path to native photosynthetic pigments.

Transient Absorption Microscopy of Layered Crystal AsSbS3.

We introduce getchellite as a new layered material for fabrication of two-dimensional van der Waals materials and heterostructures. Nanofilms of AsSbS3 were fabricated by mechanical exfoliation. Transient absorption spectroscopy measurements identified a direct bandgap at about 710 nm, which is close to the ideal single-junction photovoltaic bandgap. Transient absorption microscopy measurements with high spatial and temporal resolution were performed to reveal the spatiotemporal dynamics of photocarriers in AsSbS3. We obtained a photocarrier lifetime of about 200 ps, a diffusion coefficient of about 5 cm2 s-1, a diffusion length of about 320 nm, and a carrier mobility of about 200 cm2 V-1 s-1. These results establish AsSbS3 as a promising two-dimensional semiconductor for optoelectronic applications as an individual material or in heterostructures.

Rapid detection of flagellated and non-flagellated Salmonella by targeting the common flagellar hook gene flgE.

Salmonella spp. can cause animal and human salmonellosis. In this study, we established a simple method to detect all Salmonella species by amplifying a specific region within the flgE gene encoding the flagellar hook protein. Our preliminary sequence analysis among flagella-associated genes of Salmonella revealed that although Salmonella Gallinarum and Salmonella Pullorum are lacking flagella, they did have flagella-associated genes, including flgE. To investigate in detail, a comparative flgE sequence analysis was conducted using different bacterial strains including flagellated and non-flagellated Salmonella as well as non-Salmonella strains. Two unique regions (481-529 bp and 721-775 bp of the reference sequence) within the flgE open reading frame were found to be highly conserved and specific to all Salmonella species. Next, we designed a pair of PCR primers (flgE-UP and flgE-LO) targeting the above two regions, and performed a flgE-tailored PCR using as template DNA prepared from a total of 76 bacterial strains (31 flagellated Salmonella strains, 26 non-flagellated Salmonella strains, and 19 other non-Salmonella bacteria strains). Results showed that specific positive bands with expected size were obtained from all Salmonella (including flagellated and non-flagellated Salmonella) strains, while no specific product was generated from non-Salmonella bacterial strains. PCR products from the positive bands were confirmed by DNA sequencing. The minimum detection amount for genomic DNA and bacteria cells reached 18.3 pg/µL and 100 colony-forming unit (CFU) per PCR reaction, respectively. Using the flgE-PCR method to detect Salmonella in artificially contaminated milk samples, as low as 1 CFU/mL Salmonella was detectable after an 8-h pre-culture. Meanwhile, the flgE-tailored PCR method was applied to evaluate 247 clinical samples infected with Salmonella from different chicken breeding farms. The detection results indicated that flgE-PCR could be used to specifically detect Salmonella in concordance with the traditional bacterial culture-based detection method. It is worthwhile noticed that identification results using flgE-tailored PCR should be completed within less than 1 day, expanding the result of much faster than the standard method, which took more than 5 days. Overall, the flgE-tailored PCR method can specifically detect flagellated and non-flagellated Salmonella and can serve as a powerful tool for rapid, simple, and sensitive detection of Salmonella species. KEY POINTS : • Targeting flgE gene for all Salmonella spp. found. • The established PCR assay is used to specifically detect all Salmonella spp. • The PCR method is applied to detect clinical Salmonella spp. samples within less than 1 day.

Riley Oxidation of Heterocyclic Intermediates on Paths to Hydroporphyrins-A Review.

Riley oxidation of advanced heterocyclic intermediates (dihydrodipyrrins and tetrahydrodipyrrins) is pivotal in routes to synthetic hydroporphyrins including chlorins, bacteriochlorins, and model (bacterio)chlorophylls. Such macrocycles find wide use in studies ranging from energy sciences to photomedicine. The key transformation (-CH3 → -CHO) is often inefficient, however, thereby crimping the synthesis of hydroporphyrins. The first part of the review summarizes 12 representative conditions for Riley oxidation across diverse (non-hydrodipyrrin) substrates. An interlude summarizes the proposed mechanisms and provides context concerning the nature of various selenium species other than SeO2. The second part of the review comprehensively reports the conditions and results upon Riley oxidation of 45 1-methyltetrahydrodipyrrins and 1-methyldihydrodipyrrins. A comparison of the results provides insights into the tolerable structural features for Riley oxidation of hydrodipyrrins. In general, Riley oxidation of dihydrodipyrrins has a broad scope toward substituents, but proceeds in only modest yield. Too few tetrahydrodipyrrins have been examined to draw conclusions concerning scope. New reaction conditions or approaches will be required to achieve high yields for this critical transformation in the synthesis of hydroporphyrins.

Synthesis of the Ring C Pyrrole of Native Chlorophylls and Bacteriochlorophylls.

As part of a program to develop practical syntheses of members of the family of (bacterio)chlorophylls, two routes to 2-iodo-3-methyl-4-(3-methoxy-1,3-dioxopropyl)pyrrole, a precursor of the universal ring C, have been developed. The ß-ketoester of ring C is expected to give rise to ring E upon Knoevenagel condensation and Nazarov cyclization with a ring D constituent as demonstrated in an analogue synthesis. Two viable routes were developed beginning with N-TIPS-pyrrole or with 4-oxo-2-pentene and TosMIC, affording multi-gram-quantities of this ostensibly simple pyrrole.

Analysis of intragraft microRNA expression in a mouse-to-rat cardiac xenotransplantation model.

Xenograft rejection poses the largest obstacle to successful xenotransplantation. Recent studies have demonstrated that miRNAs play essential roles in embryogenesis, cell proliferation, and pathogenesis of human diseases. However, the role of miRNA in regulating xenograft rejection is relatively unknown. This study was undertaken to analyze the profile of intragraft miRNA expression in a heterotopic mouse-to-rat cardiac xenotransplantation model. Using microarray analysis, a total of 579 miRNAs were detected in the grafts following transplantation. When compared with syngeneic heart grafts, 24 and 25 miRNAs were found to differentially express in xenografts at 24 and 40 hours (endpoint of rejection), respectively, following transplantation. Three major miRNAs were then further analyzed, and it was found that the xenografts showed high expression of miR-146a and miR-155, but low expression of miR-451 when compared with isograft controls. This study suggests that miRNAs detected in this model are potentially involved in the xenogeneic immune response and could play an important role in regulating xenograft rejection.

[Research on the suppressive effect on transplantation rejection by indoleamine 2, 3-dioxygenase].

OBJECTIVE: To study the suppressive effect of indoleamine 2, 3-dioxygenase on transplantation rejection in mice heterotopic cardiac transplantation. METHODS: Adenovirus vector containing IDO gene was used to infect donor (C57BL/6) DC to obtain IDO(+)DC. Mouse heterotopic cardiac transplantation models were established (C57BL/6-BALB/c) and the following groups were set up, including the control group, DC injection group, TC injection group, IDO(+)DC injection group and co-injection group of IDO(+)DC and TC, 12 donors and 12 recipients in each group.Survival time of the donor heart in every group was observed. Meanwhile, donor hearts were harvested 7 days post transplantation for different examinations, including pathological examination, mRNA expression of IDO through real-time PCR, IDO protein expression through Western blot. Peripheral blood of recipients was also harvested for CD3(+)T lymphocyte apoptosis rate examination through fluorescence-activated cell sorting.One-way ANOVA and Kaplan-Meier Survival Analysis were used for statistic analysis of IDO expression, CD3(+)T lymphocyte apoptosis rate and survival time of the donor heart respectively. RESULTS: Cadiac allograft median survival time of each group were 7.0, 7.5, 11.0, 17.5, 24.0 days respectively. Compared with control and DC injection group, IDO(+)DC, TC and co-injection group significantly prolonged the survival time of donor hearts (t = 3.523-8.449, P < 0.01). Both IDO mRNA and protein expression showed significant increase(t = 5.974-16.176, P < 0.01). The CD3(+)T lymphocyte apoptosis rate was also significantly increased (t = 6.324-38.120, P < 0.01). Compared with IDO(+)DC or TC group alone, co-injection group significantly prolonged the survival time of the donor heart (t = 5.971 and 2.831, P < 0.05). Both IDO mRNA and protein expression showed significant increase (t = 2.853-15.194, P < 0.01).Furthermore, the CD3(+)T lymphocyte apoptosis rate was significantly increased as well (t = 26.069 and 7.643, P < 0.05). CONCLUSIONS: Suppressive effect of co-injection of IDO(+)DC and TC is much more effective than administration of IDO(+)DC or TC alone, which suggests that IDO achieved immune suppressive effect through the pathway of tryptophan depletion and accumulation of TC.