ObjectiveTo explore the effects of Yimei Baijiang formula （YMBJF） on colitis-associated colorectal cancer （CAC） and the nuclear factor kappaB （NF-κB） signaling pathway in mice. MethodsSixty male Balb/c mice of 4-6 weeks old were randomized into 6 groups： Normal， model， capecitabine （0.83 g·kg^-1）， and low-， medium-， and high-dose （4.63， 9.25， 18.50 g·kg^-1， respectively） YMBJF. The mouse model of CAC was established by combining azoxymethane （AOM， 10 mg·kg^-1） and dextran sulfate sodium （DSS， 2%）. At the 5^th week after the start of modeling， the capecitabine group and the YMBJF groups were respectively administrated with the corresponding doses of drugs by gavage once a day for a total of 6 weeks. The body weights and general conditions of mice were measured and observed， and the disease activity index （DAI） was scored. The tumors in the colorectal tissue were counted， and the colorectal length was measured. The histological features of the colorectal tissue in each group of mice were observed by hematoxylin-eosin （HE） staining. The levels of inflammatory cytokines including interleukin-6 （IL-6）， interleukin-1β （IL-1β）， and tumor necrosis factor-α （TNF-α） in the serum were determined by enzyme-linked immunosorbent assay （ELISA）. The expression and localization of proliferating cell nuclear antigen-67 （Ki67）， proliferating cell nuclear antigen （PCNA）， and phosphorylated nuclear transcription factor-κB p65 （p-NF-κB p65） proteins were observed by immunohistochemistry （IHC）. The apoptosis of tumor cells was observed by the TUNEL assay. The mRNA levels of IL-6，IL-1β， TNF-α， nuclear transcription factor-κB p65 （NF-κB p65）， NF-κB inhibitor alpha （IκBα）， B-cell lymphoma-2 （Bcl-2）， and Bcl-2-associated X protein （Bax） in the colorectal tissue were quantified by Real-time polymerase chain reaction（Real-time PCR）. The protein levels of NF-κB p65， phosphorylated （p）-NF-κB p65， IκBα， p-IκBα， Bcl-2， and Bax in the colorectal tissue were determined by Western blot. ResultsCompared with the model group， each YMBJF group showed decreases in DAI and tumor number （P0.01）， and the medium-dose and high-dose YMBJF groups showed increases in colorectal length （P0.05）. In addition， each YMBJF group showed alleviated colorectal mucosal pathological injury， declined levels of IL-6， IL-1β， and TNF-α in the serum （P0.05）， reduced expression of Ki67 and PCNA （P0.01）， and down-regulated expression of p-NF-κB p65 （P0.05）. The apoptosis in the medium-dose and high-dose YMBJF groups increased （P0.01）. Each YMBJF group and the capecitabine group showed down-regulated mRNA levels of IL-1β， TNF-α， IL-6， NF-κB p65， and Bcl-2 （P0.05） and up-regulated mRNA levels of IκBα and Bax （P0.05）. The mRNA level of IκBα was up-regulated， and that of Bcl-2 was down-regulated （P0.05） in the high-dose YMBJF group. The protein levels of p-IκBα and Bcl-2 were down-regulated （P0.05） in each YMBJF group. The protein levels of IκBα and Bax were up-regulated in the medium-dose and high-dose YMBJF groups （P0.01）， while those of NF-κB p65 and p-NF-κB p65 were down-regulated （P0.05）. ConclusionYMBJF can reduce the number of tumors， reduce the levels of inflammatory factors， promote tumor cell apoptosis， and inhibit tumor cell proliferation by regulating the direct effector molecules of the NF-κB signaling pathway in the mouse model of CRC.

ObjectiveTo explore the effects of Yimei Baijiang formula （YMBJF） on colitis-associated colorectal cancer （CAC） and the nuclear factor kappaB （NF-κB） signaling pathway in mice. MethodsSixty male Balb/c mice of 4-6 weeks old were randomized into 6 groups： Normal， model， capecitabine （0.83 g·kg^-1）， and low-， medium-， and high-dose （4.63， 9.25， 18.50 g·kg^-1， respectively） YMBJF. The mouse model of CAC was established by combining azoxymethane （AOM， 10 mg·kg^-1） and dextran sulfate sodium （DSS， 2%）. At the 5^th week after the start of modeling， the capecitabine group and the YMBJF groups were respectively administrated with the corresponding doses of drugs by gavage once a day for a total of 6 weeks. The body weights and general conditions of mice were measured and observed， and the disease activity index （DAI） was scored. The tumors in the colorectal tissue were counted， and the colorectal length was measured. The histological features of the colorectal tissue in each group of mice were observed by hematoxylin-eosin （HE） staining. The levels of inflammatory cytokines including interleukin-6 （IL-6）， interleukin-1β （IL-1β）， and tumor necrosis factor-α （TNF-α） in the serum were determined by enzyme-linked immunosorbent assay （ELISA）. The expression and localization of proliferating cell nuclear antigen-67 （Ki67）， proliferating cell nuclear antigen （PCNA）， and phosphorylated nuclear transcription factor-κB p65 （p-NF-κB p65） proteins were observed by immunohistochemistry （IHC）. The apoptosis of tumor cells was observed by the TUNEL assay. The mRNA levels of IL-6，IL-1β， TNF-α， nuclear transcription factor-κB p65 （NF-κB p65）， NF-κB inhibitor alpha （IκBα）， B-cell lymphoma-2 （Bcl-2）， and Bcl-2-associated X protein （Bax） in the colorectal tissue were quantified by Real-time polymerase chain reaction（Real-time PCR）. The protein levels of NF-κB p65， phosphorylated （p）-NF-κB p65， IκBα， p-IκBα， Bcl-2， and Bax in the colorectal tissue were determined by Western blot. ResultsCompared with the model group， each YMBJF group showed decreases in DAI and tumor number （P0.01）， and the medium-dose and high-dose YMBJF groups showed increases in colorectal length （P0.05）. In addition， each YMBJF group showed alleviated colorectal mucosal pathological injury， declined levels of IL-6， IL-1β， and TNF-α in the serum （P0.05）， reduced expression of Ki67 and PCNA （P0.01）， and down-regulated expression of p-NF-κB p65 （P0.05）. The apoptosis in the medium-dose and high-dose YMBJF groups increased （P0.01）. Each YMBJF group and the capecitabine group showed down-regulated mRNA levels of IL-1β， TNF-α， IL-6， NF-κB p65， and Bcl-2 （P0.05） and up-regulated mRNA levels of IκBα and Bax （P0.05）. The mRNA level of IκBα was up-regulated， and that of Bcl-2 was down-regulated （P0.05） in the high-dose YMBJF group. The protein levels of p-IκBα and Bcl-2 were down-regulated （P0.05） in each YMBJF group. The protein levels of IκBα and Bax were up-regulated in the medium-dose and high-dose YMBJF groups （P0.01）， while those of NF-κB p65 and p-NF-κB p65 were down-regulated （P0.05）. ConclusionYMBJF can reduce the number of tumors， reduce the levels of inflammatory factors， promote tumor cell apoptosis， and inhibit tumor cell proliferation by regulating the direct effector molecules of the NF-κB signaling pathway in the mouse model of CRC.

The chemical constituents of the chloroform extract of the 90% methanol extract obtained from the dried branches and leaves of Croton lauioides were investigated. By using silica gel column chromatography, C_(18 )column chromatography, MCI column chromatography, and semi-preparative high-performance liquid chromatography(HPLC), six compounds were isolated. Their structures were identified as lauioidine(1), 2α-methoxy-8α-hydroxy-6-oxogermacra-1(10),7(11)-dien-8,12-olide(2), myrrhanolide B(3), gossweilone(4), 6β,7β-epox-4α-hydroxyguaian-10-ene(5), and 4(15)-eudesmane-1β,5α-diol(6) by analyzing the HR-ESI-MS, IR, ECD, 1D NMR and 2D NMR data, as well as their physicochemical properties. All compounds were isolated from C. lauioides for the first time, among which compound 1 is a new nor-clerodane diterpenoid.
Croton/chemistry* ; Diterpenes, Clerodane/isolation & purification* ; Molecular Structure ; Drugs, Chinese Herbal/isolation & purification* ; Magnetic Resonance Spectroscopy ; Chromatography, High Pressure Liquid

This study investigated the therapeutic effects and mechanisms of Modified Yiyi Fuzi Baijiang Powder on ulcerative colitis(UC) in rats from the perspective of dampness. SD rats were randomly allocated into six groups(n=10): control, model, mesalazine, and Modified Yiyi Fuzi Baijiang Powder at low(3.96 g·kg~(-1)·d~(-1)), medium(7.92 g·kg~(-1)·d~(-1)), and high(15.84 g·kg~(-1)·d~(-1)) doses. UC was induced in all groups except the control by administration with 3% dextran sulfate sodium(DSS) solution for 7 days. The disease activity index(DAI) was recorded, and the colon tissue was collected for analysis. Histopathological changes were assessed by hematoxylin-eosin staining. Serum levels of D-lactic acid(D-LA) and diamine oxidase(DAO) were measured by ELISA. Immunohistochemistry and PCR were employed to evaluate the expression of aquaporins(AQP3, AQP4) and tight junction proteins [zonula occludens-1(ZO-1) and occludin] at both protein and mRNA levels. Compared with the control group, the model group showed an increased DAI scores(P<0.05), intestinal mucosal damage, elevated serum levels of DAO and D-LA(P<0.05), and decreased expression of AQP3, AQP4, ZO-1, and occludin(P<0.05). Treatment with Modified Yiyi Fuzi Baijiang Powder reduced the DAI scores(P<0.05), lowered the serum levels of D-LA and DAO(P<0.05), and upregulated the expression of AQP3, AQP4, ZO-1, and occludin at both protein and mRNA levels compared with the model group. These findings suggest that Modified Yiyi Fuzi Baijiang Powder exerts therapeutic effects on UC by reducing the intestinal mucosal permeability, promoting colonic mucosal repair, and regulating abnormal intestinal water metabolism, which may involve the upregulation of AQP3 and AQP4 expression.
Animals ; Colitis, Ulcerative/genetics* ; Drugs, Chinese Herbal/administration & dosage* ; Rats, Sprague-Dawley ; Rats ; Intestinal Mucosa/metabolism* ; Male ; Aquaporin 3/metabolism* ; Aquaporin 4/metabolism* ; Permeability/drug effects* ; Humans ; Powders ; Intestinal Barrier Function

Clathrin-mediated endocytosis (CME) is a critical process by which cells internalize macromolecular substances and initiate vesicle trafficking, serving as the foundation for many cellular activities. Central to this process are clathrin-coated structures (CCSs), which consist of clathrin-coated pits (CCPs) and clathrin plaques. While clathrin-coated pits are well-established in the study of endocytosis, clathrin plaques represent a more recently discovered but equally important component of this system. These plaques are large, flat, and extended clathrin-coated assemblies found on the cytoplasmic membrane. They are distinct from the more typical clathrin-coated pits in terms of their morphology, larger surface area, and longer lifespan. Recent research has revealed that clathrin plaques play roles that go far beyond endocytosis, contributing to diverse cellular processes such as cellular adhesion, mechanosensing, migration, and pathogen invasion. Unlike traditional clathrin-coated pits, which are transient and dynamic structures involved primarily in the internalization of molecules, clathrin plaques are more stable and extensive, often persisting for extended periods. Their extended lifespan suggests that they serve functions beyond the typical endocytic role, making them integral to various cellular processes. For instance, clathrin plaques are involved in the regulation of intercellular adhesion, allowing cells to better adhere to one another or to the extracellular matrix, which is crucial for tissue formation and maintenance. Furthermore, clathrin plaques act as mechanosensitive hubs, enabling the cell to sense and respond to mechanical stress, a feature that is essential for processes like migration, tissue remodeling, and even cancer progression. Recent discoveries have also highlighted the role of clathrin plaques in cellular signaling. These plaques can serve as scaffolds for signaling molecules, orchestrating the activation of various pathways that govern cellular behavior. For example, the recruitment of actin-binding proteins such as F-actin and vinculin to clathrin plaques can influence cytoskeletal dynamics, helping cells adapt to mechanical changes in their environment. This recruitment also plays a pivotal role in regulating cellular migration, which is crucial for developmental processes. Additionally, clathrin plaques influence receptor-mediated signal transduction by acting as platforms for the assembly of signaling complexes, thereby affecting processes such as growth factor signaling and cellular responses to extracellular stimuli. Despite the growing body of evidence that supports the involvement of clathrin plaques in a wide array of cellular functions, much remains unknown about the precise molecular mechanisms that govern their formation, maintenance, and turnover. For example, the factors that regulate the recruitment of clathrin and other coat proteins to form plaques, as well as the signaling molecules that coordinate plaque dynamics, remain areas of active research. Furthermore, the complex interplay between clathrin plaques and other cellular systems, such as the actin cytoskeleton and integrin-based adhesion complexes, needs further exploration. Studies have shown that clathrin plaques can respond to mechanical forces, with recent findings indicating that they act as mechanosensitive structures that help the cell adapt to changing mechanical environments. This ability underscores the multifunctional nature of clathrin plaques, which, in addition to their role in endocytosis, are involved in cellular processes such as mechanotransduction and adhesion signaling. In summary, clathrin plaques represent a dynamic and versatile component of clathrin-mediated endocytosis. They play an integral role not only in the internalization of macromolecular cargo but also in regulating cellular adhesion, migration, and signal transduction. While much has been learned about their structural and functional properties, significant questions remain regarding the molecular mechanisms that regulate their formation and their broader role in cellular physiology. This review highlights the evolving understanding of clathrin plaques, emphasizing their importance in both endocytosis and a wide range of other cellular functions. Future research is needed to fully elucidate the mechanisms by which clathrin plaques contribute to cellular processes and to better understand their implications for diseases, including cancer and tissue remodeling. Ultimately, clathrin plaques are emerging as crucial hubs that integrate mechanical, biochemical, and signaling inputs, providing new insights into cellular function and the regulation of complex cellular behaviors.

OBJECTIVE: To investigate the clinical efficacy and safety of single Kirschner wire assisted poking and closed reduction in the treatment of Gartland type Ⅲ supracondylar humeral fractures in children. METHODS: A retrospective analysis was performed on patients diagnosed with Gravland type Ⅲ supracondylar humeral fractures between January 2022 and June 2023. A total of 46 patients were treated with closed reduction assisted by Kirschner wires and percutaneous Kirschner wire internal fixation.There were 25 males and 21 females. The age ranged from 5 to 10 years old, with an average of (5.8±1.8) years old. The left side was involved in 28 patients and the right side in 18 patients. Record the operative duration for patients, the number of fluoroscopic exposures, fracture healing time, postoperative carrying angle, Baumann angle, elbow joint function score at three months post-operation, and any associated complications. RESULTS: All 46 patients were followed up for a period of 12 to 16 weeks, with an average of (13.74±1.44 )weeks. The operation duration was (30.7±5.1) minutes, the fluoroscopy count was (10.2±2.7) times, the postoperative carrying angle of the elbow joint was (8.7±2.2) degrees, and the Baumann angle was (71.5±2.9) degrees. All fractures achieved successful union in all patients, with a mean healing time of (25.5±1.7) days.At the final follow-up, elbow joint function was assessed using the Flynn criteria, with 43 patients rated as excellent and 3 patients rated as good. No complications were observed, including cubitus varus, nerve injury, or local infection. CONCLUSION The use of a single Kirschner wire assisted prying reduction for treating Gartland type Ⅲ supracondylar humeral fractures in children demonstrates excellent clinical efficacy and safety.
Humans ; Male ; Female ; Child ; Bone Wires ; Child, Preschool ; Humeral Fractures/physiopathology* ; Retrospective Studies ; Fracture Fixation, Internal/instrumentation* ; Treatment Outcome ; Fracture Healing

OBJECTIVE: To observe the clinical symptoms and MRI outcomes of patients with ruptured lumbar disc herniation(LDH) through a multicenter randomized controlled study, and to evaluate the clinical efficacy and safety of Yiqi Huoxue formula() in the treatment of this disease. METHODS: A total of 160 outpatients and inpatients with ruptured LDH admitted to 4 medical centers from January 2023 to June 2023 were selected and randomly divided into the Yiqi Huoxue formula group and the control group, with 80 patients in each group. In the Yiqi Huoxue formula group, there were 43 males and 37 females, with an age of (41.03±9.56) years and a disease duration of (10.45±25.37) days, and the patients were treated with Yiqi Huoxue formula. In the control group, there were 34 males and 46 females, with an age of (42.14±8.73) years and a disease duration of (11.31±21.14) days;during the acute phase, patients in this group could take celecoxib capsules orally, and methylcobalamin orally at the same time. The Japanese Orthopaedic Association (JOA) score, Oswestry disability index (ODI), changes in the volume of herniated disc tissue on MRI, herniation rate, and absorption rate were recorded at the time of enrollment and during follow-ups at the 3rd, 6th, and 12th month after treatment. RESULTS: A total of 156 patients completed the clinical follow-up, and 4 patients withdrew midway. The clinical symptoms of all patients who completed the study were relieved to varying degrees, and reabsorption of herniated disc tissue was observed in all patients in the Yiqi Huoxue formula group after treatment. For the JOA score:in the Yiqi Huoxue formula group, it was (10.73±2.76) points before treatment and (24.65±2.19) points at the 12th month after treatment;in the control group, it was (11.01±1.20) points before treatment and (17.07±3.26) points at the 12th month after treatment. For the ODI score:in the Yiqi Huoxue formula group, it was (26.21±3.55) points before treatment and (5.65±2.19) points at the 12th month after treatment;in the control group, it was (27.92±2.51) points before treatment and (9.09±2.15) points at the 12th month after treatment. At the 12th month after treatment, the JOA and ODI scores of both groups were better than those before treatment, and the scores of the Yiqi Huoxue formula group were better than those of the control group, with statistically significant differences (P<0.05). In terms of the herniated disc volume and herniation rate on MRI, the Yiqi Huoxue formula group was superior to the control group, with statistically significant differences(P<0.05). Reabsorption occurred in 56.96%(45/79) of patients in the Yiqi Huoxue formula group, which was significantly higher than the 37.66%(29/77) in the control group. CONCLUSION After treatment with Yiqi Huoxue formula, patients with ruptured LDH show significant improvement in clinical symptoms and a marked reduction in the volume of herniated discs. During the follow-up period, no obvious adverse drug reactions are observed in patients, and no recurrence of symptoms is found at the last follow-up, indicating that the formula has safe and reliable efficacy.
Humans ; Male ; Female ; Intervertebral Disc Displacement/drug therapy* ; Adult ; Drugs, Chinese Herbal/adverse effects* ; Middle Aged ; Lumbar Vertebrae

PURPOSE: To investigate the protective effect of sub-hypothermic mechanical perfusion combined with membrane lung oxygenation on ischemic hypoxic injury of yorkshire brain tissue caused by traumatic blood loss. METHODS: This article performed a random controlled trial. Brain tissue of 7 yorkshire was selected and divided into the sub-low temperature anterograde machine perfusion group (n = 4) and the blank control group (n = 3) using the random number table method. A yorkshire model of brain tissue injury induced by traumatic blood loss was established. Firstly, the perfusion temperature and blood oxygen saturation were monitored in real-time during the perfusion process. The number of red blood cells, hemoglobin content, NA⁺, K⁺, and Ca²⁺ ions concentrations and pH of the perfusate were detected. Following perfusion, we specifically examined the parietal lobe to assess its water content. The prefrontal cortex and hippocampus were then dissected for histological evaluation, allowing us to investigate potential regional differences in tissue injury. The blank control group was sampled directly before perfusion. All statistical analyses and graphs were performed using GraphPad Prism 8.0 Student t-test. All tests were two-sided, and p value of less than 0.05 was considered to indicate statistical significance. RESULTS: The contents of red blood cells and hemoglobin during perfusion were maintained at normal levels but more red blood cells were destroyed 3 h after the perfusion. The blood oxygen saturation of the perfusion group was maintained at 95% - 98%. NA⁺ and K⁺ concentrations were normal most of the time during perfusion but increased significantly at about 4 h. The Ca²⁺ concentration remained within the normal range at each period. Glucose levels were slightly higher than the baseline level. The pH of the perfusion solution was slightly lower at the beginning of perfusion, and then gradually increased to the normal level. The water content of brain tissue in the sub-low and docile perfusion group was 78.95% ± 0.39%, which was significantly higher than that in the control group (75.27% ± 0.55%, t = 10.49, p < 0.001), and the difference was statistically significant. Compared with the blank control group, the structure and morphology of pyramidal neurons in the prefrontal cortex and CA1 region of the hippocampal gyrus were similar, and their integrity was better. The structural integrity of granulosa neurons was destroyed and cell edema increased in the perfusion group compared with the blank control group. Immunofluorescence staining for glail fibrillary acidic protein and Iba1, markers of glial cells, revealed well-preserved cell structures in the perfusion group. While there were indications of abnormal cellular activity, the analysis showed no significant difference in axon thickness or integrity compared to the 1-h blank control group. CONCLUSIONS Mild hypothermic machine perfusion can improve ischemia and hypoxia injury of yorkshire brain tissue caused by traumatic blood loss and delay the necrosis and apoptosis of yorkshire brain tissue by continuous oxygen supply, maintaining ion homeostasis and reducing tissue metabolism level.
Animals ; Perfusion/methods* ; Disease Models, Animal ; Brain Injuries/etiology* ; Swine ; Male ; Hypothermia, Induced/methods*

OBJECTIVES: To evaluate the effectiveness of single-balloon and double-balloon enteroscopy in diagnosing pediatric small bowel diseases and assess the diagnostic efficacy of computed tomography enterography (CTE) for small bowel diseases using enteroscopy as the reference standard. METHODS: Clinical data from 576 children who underwent enteroscopy at Hunan Children's Hospital between January 2017 and December 2023 were retrospectively collected. The children were categorized based on enteroscopy type into the single-balloon enteroscopy (SBE) group (n=457) and double-balloon enteroscopy (DBE) group (n=119), and the clinical data were compared between the two groups. The sensitivity and specificity of CTE for diagnosing small bowel diseases were evaluated using enteroscopy results as the standard. RESULTS: Among the 576 children, small bowel lesions were detected by enteroscopy in 274 children (47.6%).There was no significant difference in lesion detection rates or complication rates between the SBE and DBE groups (P>0.05), but the DBE group had deeper insertion, longer procedure time, and higher complete small bowel examination rate (P<0.05). The complication rate during enteroscopy was 4.3% (25/576), with 18 cases (3.1%) of mild complications and 7 cases (1.2%) of severe complications, which improved with symptomatic treatment, surgical, or endoscopic intervention. Among the 412 children who underwent CTE, the sensitivity and specificity for diagnosing small bowel diseases were 44.4% and 71.3%, respectively. CONCLUSIONS SBE and DBE have similar diagnostic efficacy for pediatric small bowel diseases, but DBE is preferred for suspected deep small bowel lesions and comprehensive small bowel examination. Enteroscopy in children demonstrates relatively good overall safety. CTE demonstrates relatively low sensitivity but comparatively high specificity for diagnosing small bowel diseases.
Retrospective Studies ; Treatment Outcome ; Double-Balloon Enteroscopy/statistics & numerical data* ; Single-Balloon Enteroscopy/statistics & numerical data* ; Humans ; Male ; Female ; Child ; Operative Time ; Tomography, X-Ray Computed/statistics & numerical data* ; Sensitivity and Specificity ; Intestine, Small/surgery* ; Intestinal Diseases/surgery*

OBJECTIVES: To study the clinical characteristics of pediatric Behçet syndrome (BS). METHODS: A retrospective review was conducted on the medical records of children hospitalized in the Department of Pediatrics at the Second Hospital of Hebei Medical University between December 2014 and December 2024 who met diagnostic criteria for BS. RESULTS: Among 45 children with BS, 26 (58%) were male. Oral aphthous ulcers were the most common manifestation (43/45, 96%), followed by genital ulcers (23/45, 51%) and gastrointestinal involvement (18/45, 40%). Genital ulcers were more frequent in girls, whereas ocular involvement was more common in boys (P<0.05). The pathergy test was positive in 10 (22%), and HLA-B51 was positive in 13 (29%). Fecal calprotectin (FC) was elevated in 16 (36%); gastrointestinal involvement was more frequent in children with elevated FC than in those with normal FC (P<0.05). According to the respective criteria, 17 (38%) patients met the International Study Group criteria (1990), 33 (73%) met the International Criteria for Behçet Disease (2014), and 13 (29%) met the Pediatric Behçet Disease criteria (2015). CONCLUSIONS Pediatric BS shows marked clinical heterogeneity. HLA-B51 is associated with disease susceptibility.
Humans ; Behcet Syndrome/genetics* ; Male ; Female ; Child ; Retrospective Studies ; Adolescent ; Child, Preschool ; Leukocyte L1 Antigen Complex/analysis* ; HLA-B51 Antigen