Objective: To characterize perioperative dynamic changes in immune-cell phenotypes and inflammatory cytokines in patients undergoing CPB (cardiopulmonary bypass) cardiac surgery, and to explore their associations with postoperative outcomes. Methods: In this prospective cohort study, 120 adult patients who underwent elective cardiac surgery under CPB at West China Hospital from May 2022 to March 2023 were enrolled. Perioperative immune-cell phenotypes and concentrations of 40 inflammation-related cytokines were measured. The primary outcomes were the sequential organ failure assessment (SOFA) score at 24 h after surgery and ΔSOFA (the peak SOFA score within 48 h after surgery minus the preoperative SOFA score). Secondary outcomes included major adverse cardiovascular events (MACE), acute kidney injury (AKI), respiratory failure, severe liver injury, and infection. Results: The mean age of enrolled patients was 57±10 years. Of these, 52% (62/120) were male and 90% (108/120) underwent valve surgery. During the rewarming to the end of CPB, neutrophil counts rapidly increased (7.39×10 /L vs preoperative 3.07×10 /L, P<0.001), with significant upregulation of CD11b (7.30×10 /L vs preoperative 3.05×10 /L, P<0.001) and CD54 (7.15×10 /L vs preoperative 2.99×10 /L, P<0.001). Lymphocyte counts increased at the end of CPB (1.75×10 /L vs preoperative 1.12×10 /L, P<0.001) but decreased significantly at 24 h after surgery (0.59×10 /L vs preoperative 1.12×10 /L, P<0.001). Plasma analysis showed that multiple pro-inflammatory cytokines increased during CPB and remained elevated up to 24 h after surgery; five chemokines and the anti-inflammatory cytokine IL-10 peaked at the end of CPB. The SOFA score increased from 1 (1, 2) preoperatively to 7 (5, 10) at 24 h after surgery, with a ΔSOFA of 6 (4, 8). Within 30 days after surgery, 48 patients (40.0%) developed AKI, 17 (14.2%) developed infection, 4 (3.3%) developed severe liver injury, 3 (2.5%) developed respiratory failure, and 3 (2.5%) experienced MACE. During the 2-year follow-up, 8 patients (6.7%) experienced MACE and 5 (4.2%) died. Conclusion: Multi-organ dysfunction is common after cardiac surgery under CPB (median ΔSOFA, 6), accompanied by perioperative activation of multiple immune-cell subsets and upregulation of pro-inflammatory, anti-inflammatory, and chemotactic mediators. This study provides data-driven evidence and research clues for further investigation of the associations between CPB-related immune perturbations and postoperative organ dysfunction and clinical outcomes.

ObjectiveTo integrate network pharmacology prediction with multi-level experimental verification methods， and to explore in depth the therapeutic efficacy and potential mechanism of luteolin in treating gout. MethodsDatabases were used to obtain potential pharmacodynamic targets of luteolin. Protein-protein interaction （PPI） network construction and network pharmacology analysis techniques were used to screen key core targets of luteolin in gout treatment. Further biological function enrichment analysis and signaling pathway analysis were performed on these targets. Molecular docking simulation was used to calculate the binding energy between luteolin and potential core targets， clarifying the strength of their interactions. In the in vivo experiment for hyperuricemia， 48 mice were randomly divided into a blank group， a model group， an allopurinol group （5 mg·kg^-1）， and low-dose （10 mg·kg^-1）， medium-dose （30 mg·kg^-1）， and high-dose （90 mg·kg^-1） luteolin groups. For the first three days， the blank and model groups were gavaged with an equal volume of normal saline， while the allopurinol group and luteolin groups were gavaged with corresponding drugs. From day 4 onwards， modeling was performed by intraperitoneal injection at 12：00 daily （normal saline for the blank group， and oxonic acid potassium-hypoxanthine mixture for other groups， with 300 mg·kg^-1 for each group）. Gavage intervention was administered at 18：00 daily （normal saline for the blank/model groups， and corresponding drugs for the treatment groups） until day 7. After sampling， levels of serum uric acid （UA）， alanine aminotransferase （ALT）， and aspartate aminotransferase （AST） were measured. Levels of xanthine oxidase （XO） in the liver and kidney， ATP-binding cassette transporter G2 （ABCG2） and malondialdehyde （MDA） in the kidney， and superoxide dismutase （SOD） in the liver were determined. Renal HE staining was also performed. In the pharmacodynamic study of gouty arthritis， 36 rats were randomly divided into a blank group， a model group， a colchicine group （0.315 mg·kg^-1）， and low-dose （7 mg·kg^-1）， medium-dose （21 mg·kg^-1）， and high-dose （63 mg·kg^-1） luteolin groups. The model was established by vertically injecting 100 µL of 25 g·L^-1 monosodium urate suspension into the posterior lateral aspect of the right ankle joint （the blank group was injected with an equal volume of normal saline）， with repeated injections every two days for reinforcement. From day 2 after modeling， daily gavage administration was performed （normal saline for the blank/model groups， and corresponding drugs for the treatment groups） for a total of 16 days. During the experiment， ankle swelling and pain threshold were measured regularly. After sampling， levels of serum tumor necrosis factor-α （TNF-α）， interleukin-6 （IL-6）， and interleukin-1β （IL-1β） were determined. Ankle joints were subjected to HE， Masson， and safranin O-fast green staining， and HE staining was also performed on ankle synovial tissue and various organs. Western blot was used to determine the expression levels of key proteins in gout-related signaling pathways. ResultsNetwork pharmacology analysis predicted that luteolin may regulate over 20 core targets， such as XO， ABCG2， nuclear factor erythroid 2-related factor 2 （Nrf2）， and SOD， through acting on signaling pathways including NF-κB， phosphoinositide 3-kinase/protein kinase B （PI3K/Akt）， and ABC transporters， thereby affecting uric acid metabolism and inflammatory responses. In the hyperuricemia model， compared with the blank group， the model group showed significantly increased serum UA level， liver and kidney XO activity， renal ABCG2 expression， and liver SOD activity （P<0.01）. Compared with the model group， the high-dose luteolin group significantly reduced serum UA level （P<0.01）， inhibited liver and kidney XO activity （P<0.01）， and significantly increased renal ABCG2 expression and liver SOD activity （P<0.01）， effectively alleviating renal oxidative stress damage and improving renal histopathological status. In the gouty arthritis model， compared with the blank group， the model group showed significant ankle swelling， decreased pain threshold， and significantly increased levels of IL-6， IL-1β， and TNF-α in serum and synovial tissue （P<0.01）. The high-dose luteolin group significantly reduced ankle swelling， prolonged hot plate pain threshold， effectively decreased the levels of the above inflammatory factors in serum and synovial tissue （P<0.01）， and significantly improved ankle pathological damage， showing good analgesic and anti-inflammatory effects. Western blot results further confirmed that luteolin significantly upregulated Nrf2 protein expression and downregulated XO and nucleotide-binding oligomerization domain （NOD）-like receptor protein 3 （NLRP3） expression in animals. ConclusionLuteolin can improve symptoms of hyperuricemia and gouty arthritis， and its potential mechanism may be related to inhibiting XO activity， increasing ABCG2 and SOD levels， and regulating Nrf2-mediated oxidative stress-related pathways.

Stroke is the leading cause of death and disability among adults in China， and its common complications include digestive system abnormalities， cognitive impairment， depression， stroke-associated pneumonia， and hemiplegia. The combination of traditional Chinese and Western medicine has great potential in treating post-stroke complications. Xinglou Chengqitang （XLCQT） is a representative prescription of alleviating the disease in the upper part by treating the lower part. It has definite therapeutic effect and high safety. Clinically， XLCQT is often used to treat stroke and its complications. However， the quantity and quality of clinical trials of XLCQT in treating post-stroke complications need to be improved. Additionally， since the basic research is weak， the material basis and multi-target mechanism for the efficacy of this prescription are unknown. This article reviews XLCQT in terms of the pharmacodynamic basis， medicinal properties， safety evaluation， and progress in clinical research and mechanisms in treating post-stroke complications. This article summarizes 22 key active ingredients of XLCQT in treating acute stroke complicated with syndrome of phlegm heat and fu-organ excess. Among these key active ingredients， resveratrol， kaempferol， luteolin， chrysoeriol， apigenin， （+）-catechin， and adenosine have good pharmacokinetic properties and high bioavailability. The mechanisms of XLCQT in treating post-stroke complications are complex， including inflammatory response， brain-gut axis， hypothalamic-pituitary-adrenal （HPA） axis， intestinal flora， neurotrophic factors， autophagy， oxidative stress， and free radical damage. This review helps to deeply understand the pharmacodynamic basis and mechanisms of XLCQT in treating post-stroke complications and provides a theoretical basis for the clinical application of XLCQT against post-stroke complications and the development of drugs.

ObjectiveTo investigate the effect of Naoqingtong decoction （NQT） on the kidney damage and the inflammatory factors NOD-like receptor protein 3 （NLRP3）， apoptosis-associated speck-like protein containing a C-terminal caspase recruitment domain （ASC）， cysteinyl aspartate-specific proteinase-1 （Caspase-1）， interleukin-6 （IL-6）， and tumor necrosis factor-α （TNF-α） in spontaneously hypertensive rats （SHRs）. MethodsTwenty-four SHRs were randomized into a model group， a low-dose （12.9 g·kg^-1·d^-1） NQT （NQT-L） group， a high-dose （25.8 g·kg^-1·d^-1） NQT group （NQT-H）， and a captopril （CTP， 20 mg·kg^-1·d^-1） group， with 6 rats in each group. In addition， 6 homozygous male Wistar-Kyoto rats were used as the control group. The control and model groups were administrated with the same amount of normal saline by gavage for 8 weeks. General behaviors of rats were observed during the intervention period， and the blood pressure was measured periodically. At the end of intervention， the body mass was weighed， and both kidneys were collected and weighed for the calculation of the renal index. Hematoxylin-eosin staining was performed to observe the pathological changes in the kidney tissue. Real-time fluorescence quantitative polymerase chain reaction （Real-time PCR） and Western blot were employed to determine the expression levels of NLRP3， ASC， Caspase-1， IL-6， and TNF-α in the kidney tissue. ResultsDuring the experiment period， the control group had normal mental status， food intake， and activity， while the model group showed thinning of hair， loss of luster， reduced activity， loss of appetite， fecal adhesion， and irritability， and some of the skin had scratches or blood scabs. The above symptoms were alleviated to different degrees after 8 weeks of NQT administration. An intelligent non-invasive sphygmomanometer was used to measure the tail artery pressure of rats， which showed that the systolic and diastolic blood pressure of rats in the model group was higher than that in the control group （P<0.01）. Compared with the model group， drug interventions lowered the systolic and diastolic blood pressure （P<0.05， P<0.01）. Compared with the control group， the model group showed severe pathological damage in the kidney tissue， which was alleviated in each drug intervention group. Compared with the control group， the model group showed up-regulated expression levels of NLRP3， ASC， Caspase-1， IL-6， and TNF-α in the kidney tissue （P<0.05， P<0.01）. Compared with the model group， the drug intervention groups showed down-regulated expression levels of NLRP3， ASC， Caspase-1， IL-6， and TNF-α in the kidney tissue （P<0.05， P<0.01）. ConclusionNQT can lower the blood pressure in SHRs by inhibiting the activation of NLRP3 inflammasomes， suppressing renal inflammation， and ameliorating hypertensive kidney damage.

The innate immune system can be boosted in response to subsequent triggers by pre-exposure to microbes or microbial products, known as “trained immunity”. Compared to classical immune memory, innate trained immunity has several different features. Firstly, the molecules involved in trained immunity differ from those involved in classical immune memory. Innate trained immunity mainly involves innate immune cells (e.g., myeloid immune cells, natural killer cells, innate lymphoid cells) and their effector molecules (e.g., pattern recognition receptor (PRR), various cytokines), as well as some kinds of non-immune cells (e.g., microglial cells). Secondly, the increased responsiveness to secondary stimuli during innate trained immunity is not specific to a particular pathogen, but influences epigenetic reprogramming in the cell through signaling pathways, leading to the sustained changes in genes transcriptional process, which ultimately affects cellular physiology without permanent genetic changes (e.g., mutations or recombination). Finally, innate trained immunity relies on an altered functional state of innate immune cells that could persist for weeks to months after initial stimulus removal. An appropriate inducer could induce trained immunity in innate lymphocytes, such as exogenous stimulants (including vaccines) and endogenous stimulants, which was firstly discovered in bone marrow derived immune cells. However, mature bone marrow derived immune cells are short-lived cells, that may not be able to transmit memory phenotypes to their offspring and provide long-term protection. Therefore, trained immunity is more likely to be relied on long-lived cells, such as epithelial stem cells, mesenchymal stromal cells and non-immune cells such as fibroblasts. Epigenetic reprogramming is one of the key molecular mechanisms that induces trained immunity, including DNA modifications, non-coding RNAs, histone modifications and chromatin remodeling. In addition to epigenetic reprogramming, different cellular metabolic pathways are involved in the regulation of innate trained immunity, including aerobic glycolysis, glutamine catabolism, cholesterol metabolism and fatty acid synthesis, through a series of intracellular cascade responses triggered by the recognition of PRR specific ligands. In the view of evolutionary, trained immunity is beneficial in enhancing protection against secondary infections with an induction in the evolutionary protective process against infections. Therefore, innate trained immunity plays an important role in therapy against diseases such as tumors and infections, which has signature therapeutic effects in these diseases. In organ transplantation, trained immunity has been associated with acute rejection, which prolongs the survival of allografts. However, trained immunity is not always protective but pathological in some cases, and dysregulated trained immunity contributes to the development of inflammatory and autoimmune diseases. Trained immunity provides a novel form of immune memory, but when inappropriately activated, may lead to an attack on tissues, causing autoinflammation. In autoimmune diseases such as rheumatoid arthritis and atherosclerosis, trained immunity may lead to enhance inflammation and tissue lesion in diseased regions. In Alzheimer’s disease and Parkinson’s disease, trained immunity may lead to over-activation of microglial cells, triggering neuroinflammation even nerve injury. This paper summarizes the basis and mechanisms of innate trained immunity, including the different cell types involved, the impacts on diseases and the effects as a therapeutic strategy to provide novel ideas for different diseases.

ObjectiveTo explore effect of Xianlian Jiedu prescription on the recurrence of colorectal cancer （CRC） and investigate the related mechanisms. MethodsA postoperative recurrence model was established in 25 Balb/c mice by injecting CT26 cells subcutaneously into the armpit， followed by surgical removal of 99% of the subcutaneous tumor. The mice were randomly divided into model group， low-dose Xianlian Jiedu prescription （XLJDP-L） group （6.45 g·kg^-1·d^-1）， medium-dose Xianlian Jiedu prescription （XLJDP-M） group （12.9 g·kg^-1·d^-1）， high-dose Xianlian Jiedu prescription （XLJDP-H） group （25.8 g·kg^-1·d^-1）， and 5-fluorouracil （5-FU） group （1×10^-3 g·kg^-1·d^-1）. The mice were euthanized after 14 days of continuous intervention， and recurrent tumor tissue was harvested. Hematoxylin and eosin （HE） staining was used to observe pathological and morphological changes in the recurrent tumor tissue. Immunohistochemistry （IHC） was employed to assess the expression of proliferating cell nuclear antigen （Ki67）， vascular endothelial growth factor （VEGF）， and platelet-endothelial cell adhesion molecule （CD31） in recurrent tumor tissue. The Western blot was used to detect the protein expression levels of angiopoietin-2 （ANG-2）， VEGF， phosphorylated-protein kinase B （p-Akt）， protein kinase B （Akt）， phosphorylated-phosphatidylinositol 3-kinase （p-PI3K）， and phosphatidylinositol 3-kinase （PI3K） in recurrent tumor tissue. ResultsBefore treatment， there were no statistical differences in tumor volume， tumor weight， and body mass among the XLJDP-L， XLJDP-M， and XLJDP-H groups and the 5-FU group compared to the model group， indicating model stability. After treatment， compared with those in the model group， the tumor volume and tumor weight in the XLJDP-L， XLJDP-M， and XLJDP-H groups and the 5-FU group were significantly reduced （P<0.01）， showing dose dependency. Meanwhile， there were no significant differences in body weight among the XLJDP-L， XLJDP-M， and XLJDP-H groups and the 5-FU group compared to the model group. HE staining showed that compared with that in the model group， tumor tissue in the XLJDP-L， XLJDP-M， and XLJDP-H groups and the 5-FU group had loosely arranged cells， increased intercellular spaces， small and shriveled nuclei， light staining， fewer mitotic figures and atypical nuclei， and increased necrotic areas. IHC showed that compared with those of the model group， the positive rates of Ki67， VEGF， and CD31 in the recurrent tumor tissue of the XLJDP-L， XLJDP-M， and XLJDP-H groups and the 5-FU group were significantly reduced （P<0.01） in a dose-dependent manner. Western blot results showed that compared with those of the model group， the protein expression levels of ANG-2 and VEGF in the recurrent tumor tissue of the XLJDP-L， XLJDP-M， and XLJDP-H groups and the 5-FU group were significantly downregulated （P<0.05， P<0.01）， and the p-Akt/Akt and p-PI3K/PI3K ratios were significantly decreased in a dose-dependent manner （P<0.05， P<0.01）. ConclusionXianlian Jiedu prescription significantly inhibits the recurrence of CRC in mice after subcutaneous tumor surgery. The mechanism may involve regulating the PI3K/Akt pathway and downregulating key angiogenic proteins such as ANG-2， VEGF， and CD31.

ObjectiveTo investigate the mechanism by which Huanglian Jiedutang （HLJDT） inhibits pyroptosis and neuroinflammation in Alzheimer's disease （AD） mice via the NOD-like receptor protein 3 （NLRP3）/cysteinyl aspartate-specific protease-1 （Caspase）-1/gasdermin D （GSDMD） pathway. MethodsThirty APP/PS1 double transgenic mice were randomly and evenly divided into the model group （model group）， the positive control group （Donepezil group， 0.65 mg·kg^-1）， and the HLJDT treatment group （HLJDT group， 5.2 g·kg^-1）. Ten C57BL/6 mice were assigned to the blank control group （control group）. The Morris water maze and novel object recognition tests were used to evaluate learning and memory abilities. Nissl staining was employed to observe the morphology， quantity， and distribution of neurons in the hippocampal region. Golgi staining was used to examine the morphology and density of neuronal dendritic spines in the hippocampus. Real-time quantitative polymerase chain reaction （Real-time PCR） was performed to detect the mRNA expression of neuroinflammation-related factors and genes in the NLRP3/Caspase-1/GSDMD pyroptosis pathway in the hippocampus. Western blot was used to detect the expression of postsynaptic density protein 95 （PSD95）， amyloid precursor protein （APP）， inflammatory factors including nuclear factor-κB （NF-κB）， phosphorylated NF-κB （p-NF-κB）， tumor necrosis factor-α （TNF-α）， interleukin-1β （IL-1β）， as well as pyroptosis pathway-related proteins including NLRP3， Caspase-1， GSDMD， and GSDMD-N. ResultsCompared with the control group， the model group exhibited significantly decreased learning and memory abilities （P<0.01）， reduced numbers of neurons in the hippocampal CA3 region and dendritic spines in the hippocampal CA1 region （P<0.01）， and significantly increased hippocampal mRNA expression levels of NLRP3， Caspase-1， GSDMD， NF-κB， TNF-α， IL-1β， and IL-18 （P<0.01）. Protein levels of PSD95 were markedly decreased， while the expression levels of NLRP3， Caspase-1， GSDMD， p-NF-κB/NF-κB， TNF-α， IL-1β， and APP were significantly elevated （P<0.01）. Compared with the model group， both the Donepezil and HLJDT groups showed significantly improved learning and memory abilities （P<0.05， P<0.01）， increased numbers of hippocampal neurons in the hippocampal CA3 region and dendritic spines in the hippocampal CA1 region （P<0.01）， and significantly decreased hippocampal mRNA expression levels of NLRP3， Caspase-1， GSDMD， NF-κB， TNF-α， IL-1β， and IL-18 （P<0.05， P<0.01）. Protein levels of NLRP3， Caspase-1， GSDMD， p-NF-κB/NF-κB， TNF-α， IL-1β， and APP were significantly downregulated， while PSD95 expression was significantly upregulated （P<0.05， P<0.01）. There was no statistically significant difference in GSDMD-N levels in the Donepezil group， while GSDMD-N expression was significantly decreased in the HLJDT group （P<0.05）. ConclusionThis study confirms that HLJDT can improve learning and memory abilities in APP/PS1 double transgenic mice， and attenuate neuronal loss and synaptic damage， possibly through inhibition of pyroptosis via the NLRP3/Caspase-1/GSDMD pathway.

ObjectiveTo investigate the mechanism by which Huanglian Jiedutang （HLJDT） inhibits pyroptosis and neuroinflammation in Alzheimer's disease （AD） mice via the NOD-like receptor protein 3 （NLRP3）/cysteinyl aspartate-specific protease-1 （Caspase）-1/gasdermin D （GSDMD） pathway. MethodsThirty APP/PS1 double transgenic mice were randomly and evenly divided into the model group （model group）， the positive control group （Donepezil group， 0.65 mg·kg^-1）， and the HLJDT treatment group （HLJDT group， 5.2 g·kg^-1）. Ten C57BL/6 mice were assigned to the blank control group （control group）. The Morris water maze and novel object recognition tests were used to evaluate learning and memory abilities. Nissl staining was employed to observe the morphology， quantity， and distribution of neurons in the hippocampal region. Golgi staining was used to examine the morphology and density of neuronal dendritic spines in the hippocampus. Real-time quantitative polymerase chain reaction （Real-time PCR） was performed to detect the mRNA expression of neuroinflammation-related factors and genes in the NLRP3/Caspase-1/GSDMD pyroptosis pathway in the hippocampus. Western blot was used to detect the expression of postsynaptic density protein 95 （PSD95）， amyloid precursor protein （APP）， inflammatory factors including nuclear factor-κB （NF-κB）， phosphorylated NF-κB （p-NF-κB）， tumor necrosis factor-α （TNF-α）， interleukin-1β （IL-1β）， as well as pyroptosis pathway-related proteins including NLRP3， Caspase-1， GSDMD， and GSDMD-N. ResultsCompared with the control group， the model group exhibited significantly decreased learning and memory abilities （P<0.01）， reduced numbers of neurons in the hippocampal CA3 region and dendritic spines in the hippocampal CA1 region （P<0.01）， and significantly increased hippocampal mRNA expression levels of NLRP3， Caspase-1， GSDMD， NF-κB， TNF-α， IL-1β， and IL-18 （P<0.01）. Protein levels of PSD95 were markedly decreased， while the expression levels of NLRP3， Caspase-1， GSDMD， p-NF-κB/NF-κB， TNF-α， IL-1β， and APP were significantly elevated （P<0.01）. Compared with the model group， both the Donepezil and HLJDT groups showed significantly improved learning and memory abilities （P<0.05， P<0.01）， increased numbers of hippocampal neurons in the hippocampal CA3 region and dendritic spines in the hippocampal CA1 region （P<0.01）， and significantly decreased hippocampal mRNA expression levels of NLRP3， Caspase-1， GSDMD， NF-κB， TNF-α， IL-1β， and IL-18 （P<0.05， P<0.01）. Protein levels of NLRP3， Caspase-1， GSDMD， p-NF-κB/NF-κB， TNF-α， IL-1β， and APP were significantly downregulated， while PSD95 expression was significantly upregulated （P<0.05， P<0.01）. There was no statistically significant difference in GSDMD-N levels in the Donepezil group， while GSDMD-N expression was significantly decreased in the HLJDT group （P<0.05）. ConclusionThis study confirms that HLJDT can improve learning and memory abilities in APP/PS1 double transgenic mice， and attenuate neuronal loss and synaptic damage， possibly through inhibition of pyroptosis via the NLRP3/Caspase-1/GSDMD pathway.

Background: The immune system plays a critical role in the development and progression of osteoporosis and fractures. However, the causal relationships between antibody immune responses, immune cells, and these bone conditions remain unclear. This study aimed to explore these relationships using Mendelian randomization (MR) analysis. Methods: We collected complete blood count data from patients with fractures and healthy individuals and analyzed their differences. Then, we conducted a 2-sample, 2-step MR analysis to investigate the causal effects of antibody immune responses on osteoporosis and fractures, using inverse-variance weighted (IVW) as the primary method. We also explored whether immune cells mediate the pathway between antibodies and osteoporosis or fractures. Finally, we analyzed the functions and expression levels of key genes involved. Results: Overall, the fracture group exhibited increased white blood cell count, absolute neutrophil count, absolute monocyte count, platelet count, and their respective proportions, while absolute lymphocyte count, absolute eosinophil count, absolute basophil count, red blood cell count, and their proportions were decreased. We identified 44 causal relationships between antibodies and osteoporosis or fractures, with 7 supported by multiple MR methods, and 5 showing odds ratios significantly deviating from 1 in the IVW analysis. Epstein-Barr virus-related antibodies had a notable impact on osteoporosis and fractures. The human leukocyte antigen (HLA) gene family, particularly HLA-DPB1, emerged as a significant risk factor. However, immune cells were not found to mediate these effects. Conclusions This study elucidated the causal relationships between antibody immune responses, immune cells, and osteoporosis or fractures. The HLA gene family plays a crucial role in the interaction between antibodies and these bone conditions, with HLA-DPB1 identified as a key risk gene. Immune cells do not serve as mediators in this process. These findings provide valuable insights for future research.

Background: The immune system plays a critical role in the development and progression of osteoporosis and fractures. However, the causal relationships between antibody immune responses, immune cells, and these bone conditions remain unclear. This study aimed to explore these relationships using Mendelian randomization (MR) analysis. Methods: We collected complete blood count data from patients with fractures and healthy individuals and analyzed their differences. Then, we conducted a 2-sample, 2-step MR analysis to investigate the causal effects of antibody immune responses on osteoporosis and fractures, using inverse-variance weighted (IVW) as the primary method. We also explored whether immune cells mediate the pathway between antibodies and osteoporosis or fractures. Finally, we analyzed the functions and expression levels of key genes involved. Results: Overall, the fracture group exhibited increased white blood cell count, absolute neutrophil count, absolute monocyte count, platelet count, and their respective proportions, while absolute lymphocyte count, absolute eosinophil count, absolute basophil count, red blood cell count, and their proportions were decreased. We identified 44 causal relationships between antibodies and osteoporosis or fractures, with 7 supported by multiple MR methods, and 5 showing odds ratios significantly deviating from 1 in the IVW analysis. Epstein-Barr virus-related antibodies had a notable impact on osteoporosis and fractures. The human leukocyte antigen (HLA) gene family, particularly HLA-DPB1, emerged as a significant risk factor. However, immune cells were not found to mediate these effects. Conclusions This study elucidated the causal relationships between antibody immune responses, immune cells, and osteoporosis or fractures. The HLA gene family plays a crucial role in the interaction between antibodies and these bone conditions, with HLA-DPB1 identified as a key risk gene. Immune cells do not serve as mediators in this process. These findings provide valuable insights for future research.