Lipoprotein A (LPA) is a type of particle similar to low-density lipoprotein (LDL) that is considered one of the risk factors for cardiovascular disease (CVD), such as atherosclerosis, coronary heart disease, stroke, etc ^[1]. LP(a) is similar in size and lipid content to LDL (low-density lipoprotein) and also contains the lipoprotein ApoB-100. However, unlike LDL, LP(a) additionally contains a variable-length lipoprotein called Apo(a), which covalently binds to ApoB-100 through a single disulfide bond. LP(a) plays an important role in systemic lipid transport, guiding inflammatory cells into blood vessel walls and leading to smooth muscle cell proliferation. Furthermore, it is involved in wound healing and tissue repair, interacting with the components of blood vessel walls and the extracellular matrix ^[2]. However, LP(a) can also cause arterial narrowing by adhering to the arterial wall, accelerating the formation of blood clots, and thereby triggering a series of pathological changes related to coronary heart disease, cardiovascular disease, atherosclerosis, thrombus formation, and stroke ^[3]. The plasma concentration of LP(a) is closely related to genetic factors and is primarily regulated by the LPA gene. Therefore, the LPA gene is an important potential target for cardiovascular disease treatment. The LPA gene encodes a serine protease that inhibits the activity of tissue-type plasminogen activator I. Fragments of this protein, generated through protein hydrolysis, can adhere to atherosclerotic lesions in arteries, promoting blood clot formation. The LPA gene is expressed in both humans and non-human primates but is not expressed in mice. Constructing mouse models expressing the human LPA gene is of significant importance for developing lipid-lowering drugs, which can drive the development of novel therapies for cardiovascular diseases. Currently, various novel therapies targeting the transcription rate of the LPA gene are under development, including small interfering RNA (siRNA) and antisense oligonucleotides (ASO) ^[4]. Proprotein convertase subtilisin/kexin 9 (PCSK9) is a serine protease primarily produced in the liver but expressed in other tissues, including the intestine, heart, and neurons. The N-terminal domain of the PCSK9 protein is responsible for protein localization and stability, while the C-terminal domain is responsible for protein enzymatic activity ^[5]. The Low-density lipoprotein receptor (LDLR) is a receptor that is responsible for clearing low-density lipoprotein cholesterol (LDL-C) from the blood. PCSK9 cleaves the intracellular domain of LDLR on the cell surface, causing it to detach from the cell membrane and be transported to the lysosome for degradation, promoting LDLR degradation, and increasing plasma LDL-C. Overexpression or gain-of-function mutations of the PCSK9 gene can lead to LDL-C accumulation by reducing LDLR levels. This can cause hypercholesterolemia, which increases the risk of cardiovascular diseases, such as atherosclerosis and coronary heart disease, and neurodegenerative diseases, such as Alzheimer's disease ^[6]. PCSK9 has emerged as a key target for the development of lipid-lowering drugs. Several PCSK9-targeted antibodies or small nucleic acid drugs have been approved for marketing worldwide, including evolocumab from Amgen, alirocumab from Sanofi and Regeneron, and inclisiran from Novartis. These drugs primarily work by inhibiting PCSK9 activity or preventing PCSK9 protein from binding to LDLR, lowering LDL-C levels in the blood to treat hypercholesterolemia ^[7-8]. In addition, PCSK9 can promote tumor growth and development by regulating cell proliferation, migration, and invasion. It can also regulate the expression of inflammatory factors that contribute to inflammation. Therefore, targeting the expression of PCSK9 has been investigated in tumor immunotherapy and autoimmune disease therapy ^[9-10]. The B6-hLPA (CKI)/Alb-cre/hPCSK9 mouse model is generated by crossing B6-hLPA (CKI) mice (Catalog No.: C001521, a mouse strain with conditional expression of the human LPA gene), Alb-Cre mice (liver-specific Cre-expressing mice), and B6-hPCSK9 mice (Catalog No.: C001617). This model harbors two cardiovascular disease risk factors, namely Lp (a) (lipoprotein (a)) and PCSK9, making it suitable for research on hyperlipidemia, stroke, coronary heart disease, and other atherosclerotic cardiovascular diseases (ASCVD).

Proprotein convertase subtilisin/kexin 9 (PCSK9) is a serine protease primarily produced in the liver but expressed in other tissues, including the intestine, heart, and neurons. The N-terminal domain of the PCSK9 protein is responsible for protein localization and stability, while the C-terminal domain is responsible for protein enzymatic activity ^[1]. The Low-density lipoprotein receptor (LDLR) is a receptor that is responsible for clearing low-density lipoprotein cholesterol (LDL-C) from the blood. PCSK9 cleaves the intracellular domain of LDLR on the cell surface, causing it to detach from the cell membrane and be transported to the lysosome for degradation, promoting LDLR degradation, and increasing plasma LDL-C. Overexpression or gain-of-function mutations of the PCSK9 gene can lead to LDL-C accumulation by reducing LDLR levels. This can cause hypercholesterolemia, which increases the risk of cardiovascular diseases, such as atherosclerosis and coronary heart disease, and neurodegenerative diseases, such as Alzheimer's disease ^[2]. PCSK9 has become an important target for the development of lipid-lowering drugs. Several PCSK9-targeted antibodies or small nucleic acid drugs have been approved for marketing worldwide, including evolocumab from Amgen, alirocumab from Sanofi and Regeneron, and inclisiran from Novartis. These drugs primarily work by inhibiting PCSK9 activity or preventing PCSK9 protein from binding to LDLR, lowering LDL-C levels in the blood to treat hypercholesterolemia ^[3-4]. In addition, PCSK9 can promote tumor growth and development by regulating cell proliferation, migration, and invasion. It can also regulate the expression of inflammatory factors that contribute to inflammation. Therefore, targeting the expression of PCSK9 has been investigated in tumor immunotherapy and autoimmune disease therapy ^[5-6]. Apolipoprotein E (ApoE) is a lipid particle-associated polymorphic carrier protein encoded by the APOE gene. It is a core component of plasma lipoproteins, participating in the production, transport, and clearance of lipoproteins. ApoE is associated with chylomicrons, chylomicron remnants, high-density lipoprotein (HDL), very low-density lipoprotein (VLDL), and intermediate-density lipoprotein (IDL), especially showing preferential binding to HDL ^[7]. ApoE is the most important lipid transport protein in the body, having a profound impact on lipid metabolism. The interaction of ApoE with the low-density lipoprotein receptor (LDLR) is essential for the normal processing (catabolism) of triglyceride-rich lipoproteins ^[8]. In peripheral tissues, ApoE is primarily produced by the liver and macrophages and mediates cholesterol metabolism. In the central nervous system, ApoE is produced mainly by astrocytes and is the major cholesterol carrier in the brain. ApoE is essential for transporting cholesterol from astrocytes to neurons ^[7-10]. In addition, ApoE forms a complex with activated C1q, becoming a checkpoint inhibitor target of the classical complement pathway ^[11]. Polymorphisms of the APOE are associated with Alzheimer's disease and lipid accumulation, hyperlipidemia, atherosclerosis, high cholesterolemia, etc., and are related to the risk of various cardiovascular diseases. The B6-hPCSK9/Apoe KO mice are obtained by crossing B6-hPCSK9 mice (Catalog No.: I001179) with B6J-Apoe KO mice (Catalog No.: C001507). B6J-Apoe KO mice exhibit elevated cholesterol levels and spontaneous atherosclerosis phenotypes due to the disruption of ApoE protein synthesis, further exacerbated under a high-fat diet (HFD). On the other hand, B6-hPCSK9 mice have the mouse Pcsk9 gene sequence replaced with the human PCSK9 gene sequence through gene editing technology, expressing the human PCSK9 protein. They can be used for the development of PCSK9-targeted drugs in hyperlipidemia, stroke, coronary heart disease, and other atherosclerotic cardiovascular diseases (ASCVD). The B6-hPCSK9/Apoe KO mice, while expressing the human PCSK9 protein, exhibit significantly elevated cholesterol levels and spontaneous atherosclerosis characteristics. These mice provide an ideal platform for the PCSK9-targeted drug development in hyperlipidemia and cardiovascular diseases, demonstrating good clinical and pathological relevance.

Cluster of Differentiation 3 (CD3) is a protein complex that functions as a co-receptor on T cells, playing a critical role in the activation of cytotoxic T lymphocytes (CTLs) and helper T cells (THs). CD3 comprises five transmembrane polypeptide chains—γ, δ, ε, ζ, and η—each contributing to the structural integrity and signaling capacity of the complex. The transmembrane domains of CD3 form salt bridges with the transmembrane regions of the T cell receptor (TCR) α and β chains, assembling into the TCR-CD3 complex that mediates antigen recognition by T cells ^[1-2]. Upon antigen engagement by the TCR, activation signals are transduced intracellularly via CD3. CD3 is expressed with high specificity throughout all stages of T cell development and is therefore widely utilized as an immunohistochemical marker for T cell identification. Moreover, CD3 is present in nearly all T cell lymphomas and leukemias, enabling differential diagnosis from morphologically similar B cell and myeloid malignancies. Given its pivotal role in T cell activation and antigen recognition, CD3 has emerged as a key therapeutic target in immunosuppressive strategies for type 1 diabetes and other autoimmune disorders ^[3]. The B2M gene encodes β2-microglobulin, a serum protein that associates with the heavy chain of major histocompatibility complex (MHC) class I molecules and is essential for their surface expression on virtually all nucleated cells. Human leukocyte antigens (HLAs), also referred to as MHC molecules, are cell-surface proteins responsible for antigen presentation. The HLA system comprises class I, class II, and class III molecules. HLA class I molecules—including HLA-A, HLA-B, and HLA-C—primarily present antigens to CD8⁺ T cells and are central to immune surveillance. Through HLA class I–mediated antigen presentation, the immune system can detect aberrant peptides and initiate targeted cytotoxic responses for immune clearance. HLA-A2.1 is a subtype of HLA class I and represents one of the most prevalent HLA alleles worldwide. The B6-hCD3/H11-hB2M&HLA-A2.1 mouse model is generated by crossing B6-hCD3 mice (catalog no. C001325) with H11-hB2M&HLA-A2.1 mice (catalog no. I001138). These mice co-express human CD3, human β2-microglobulin, and HLA-A0201 proteins in vivo. This model enables mechanistic investigation of T cell activation, antigen recognition, and antigen presentation, and serves as a versatile platform for evaluating immunosuppressive therapies in autoimmune diseases, studying human viral infections, and developing and testing novel viral vaccines.

PD-1 and CTLA-4 are checkpoint receptors that critically modulate T cell immunity. The genes PDCD1 and CTLA4 encode PD-1 and CTLA-4 respectively, with CTLA4 expression largely restricted to T cells, while PDCD1 is evident in activated T cells, B cells, and myeloid populations ^[1]. These transmembrane proteins function as key negative regulators of T cell activation ^[2]. CTLA-4 primarily operates in lymphoid tissues during early immune responses to restrain T cell proliferation, whereas PD-1 predominantly acts in peripheral tissues during the effector phase to dampen T cell activity and limit immunopathology, particularly in chronically stimulated or ‘exhausted’ T cells ^[2-3]. Aberrant regulation of PD-1 and CTLA-4 is implicated in the pathogenesis of cancers, including melanoma, non-small cell lung cancer, and renal cell carcinoma, as well as chronic viral infections such as hepatitis B and C ^[1][4]. Clinically, monoclonal antibodies targeting CTLA-4 (e.g., ipilimumab) and PD-1 (e.g., nivolumab, pembrolizumab) are established immunotherapeutic agents that enhance anti-tumor responses. By blocking these negative signaling pathways, these monoclonal antibodies restore the anti-tumor activity of T cells, significantly enhancing anti-tumor responses ^[1-2]. These drug applications have not only improved the treatment outcomes for various cancers but also offer new strategies for the treatment of chronic viral infections. B6-hPD-1/hCTLA4 mouse is a dual humanized model of PD1 and CTLA4 constructed by humanizing the mouse Pdcd1 gene based on the CTLA4 humanized mouse model (Catalog No. C001413), due to the fact that the mouse Pdcd1 gene and Ctla4 gene are on the same chromosome. These mice express human CTLA4 and PDCD1 genomic sequences under the control of mouse promoters. This model is capable of reproducing the human PD-1/CTLA4 signaling pathway and is a valuable tool for studying cancers and chronic viral infections. Furthermore, this model provides a powerful preclinical research platform for evaluating the efficacy and mechanism of therapeutic drugs targeting the PD-1/CTLA4 signaling pathway.

Cluster of differentiation 3 (CD3) is a multimeric protein complex that is essential for T cell activation and antigen recognition. It consists of five different polypeptide chains (γ, δ, ε, ζ, and η) that are noncovalently associated with the T cell receptor (TCR). The TCR is responsible for recognizing antigens presented by antigen-presenting cells (APCs), while CD3 transduces the activation signal into the T cell and activates helper T-cells and cytotoxic T-cells ^[1-2]. The CD3-TCR complex is expressed on the surface of all mature T cells, and its assembly is required for T cell development and function. CD3 plays a crucial role in stabilizing the TCR and facilitating its interaction with antigens. It also recruits signaling molecules to the TCR, which initiates a cascade of events that leads to T cell activation. CD3 is a highly specific T cell marker, and its expression is increased upon T cell activation. This makes it a valuable tool for identifying and characterizing T cells in tissues and blood samples. CD3 staining is also used to diagnose T-cell lymphomas and leukemias. Due to its essential role in T cell activation, CD3 is a promising target for immunosuppressive therapy. Several anti-CD3 monoclonal antibodies have been developed and are being tested in clinical trials for the treatment of autoimmune diseases, such as type 1 diabetes and rheumatoid arthritis ^[3]. The CD19 gene encodes a member of the immunoglobulin gene superfamily. As a key co-receptor in the B cell receptor (BCR) signaling pathway, it is crucial for B cell development, activation, and differentiation. CD19, a pan-B-cell marker exclusively expressed in the B cell lineage, remains stable throughout B cell development, from pro-B cells to mature and memory B cells. It acts as a positive regulator of BCR signal transduction by forming a B cell-specific signaling complex with CD21 (complement receptor 2), CD81 (tetraspanin), and CD225 (Leu13), which lowers the threshold for antigen-induced B cell activation ^[4]. Dysregulation of CD19 is strongly linked to autoimmune diseases such as systemic lupus erythematosus (SLE) and B cell malignancies like acute lymphoblastic leukemia (ALL) and non-Hodgkin lymphoma. Mutations in this gene are associated with common variable immunodeficiency 3 (CVID3), characterized by impaired B cell differentiation and hypogammaglobulinemia. Owing to its B cell-specific expression, CD19 has become a pivotal target for immunotherapy. For example, anti-CD19 CAR-T cell therapy (e.g., Tisagenlecleucel) has shown remarkable efficacy in refractory or relapsed ALL ^[5]. Recent studies have also explored CD19-targeted bispecific antibodies (e.g., blinatumomab) to enhance tumor cell clearance ^[6]. The TNFRSF17 gene, also known as BCMA, encodes a protein belonging to the tumor necrosis factor receptor superfamily. This protein is predominantly expressed in mature B lymphocytes, particularly plasma cells, with lower expression in early B cells and non-B cells ^[7-8]. As a type III transmembrane glycoprotein, TNFRSF17 plays a critical role in B cell survival and differentiation, acting as a key regulator of B cell maturation ^[8]. Functionally, TNFRSF17 primarily acts as a receptor for the B cell-activating factor (BAFF). Upon BAFF binding, it activates both the classical NF-κB pathway and the non-classical MAPK8/JNK pathway, subsequently regulating downstream gene expression to promote B cell survival, proliferation, and antibody secretion. Furthermore, TNFRSF17 can interact with TNFR-associated factors (TRAFs) 1, 2, and 3, further mediating physiological processes related to cell differentiation and growth ^[7-8]. Multiple studies have demonstrated that the TNFRSF17 gene and its protein are associated with various B cell-related diseases. Notably, this gene exhibits abnormally high expression in diseases such as multiple myeloma and systemic lupus erythematosus, rendering it a potential therapeutic target for these conditions ^[9-10]. The B6-hCD3/hCD19/hBCMA mouse is a tri-gene humanized model generated by crossing B6-hCD3 mice (Catalog No.: C001325), B6-hCD19 mice (Catalog No.: C001731), and B6-hBCMA (hTNFRSF17) mice (Catalog No.: C001630). This model can be used for the research of autoimmune diseases such as systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA), as well as B-cell malignancies, and for the development, screening, and preclinical evaluation of related targeted therapeutics.

Cluster of differentiation 3 (CD3) is a multimeric protein complex that is essential for T cell activation and antigen recognition. It consists of five different polypeptide chains (γ, δ, ε, ζ, and η) that are noncovalently associated with the T cell receptor (TCR). The TCR is responsible for recognizing antigens presented by antigen-presenting cells (APCs), while CD3 transduces the activation signal into the T cell and activates helper T-cells and cytotoxic T-cells ^[1-2]. The CD3-TCR complex is expressed on the surface of all mature T cells, and its assembly is required for T cell development and function. CD3 plays a crucial role in stabilizing the TCR and facilitating its interaction with antigens. It also recruits signaling molecules to the TCR, which initiates a cascade of events that leads to T cell activation. CD3 is a highly specific T cell marker, and its expression is increased upon T cell activation. This makes it a valuable tool for identifying and characterizing T cells in tissues and blood samples. CD3 staining is also used to diagnose T-cell lymphomas and leukemias. Due to its essential role in T cell activation, CD3 is a promising target for immunosuppressive therapy. Several anti-CD3 monoclonal antibodies have been developed and are being tested in clinical trials for the treatment of autoimmune diseases, such as type 1 diabetes and rheumatoid arthritis ^[3]. The CD19 gene encodes a member of the immunoglobulin gene superfamily. As a key co-receptor in the B cell receptor (BCR) signaling pathway, it is crucial for B cell development, activation, and differentiation. CD19, a pan-B-cell marker exclusively expressed in the B cell lineage, remains stable throughout B cell development, from pro-B cells to mature and memory B cells. It acts as a positive regulator of BCR signal transduction by forming a B cell-specific signaling complex with CD21 (complement receptor 2), CD81 (tetraspanin), and CD225 (Leu13), which lowers the threshold for antigen-induced B cell activation ^[4]. Dysregulation of CD19 is strongly linked to autoimmune diseases such as systemic lupus erythematosus (SLE) and B cell malignancies like acute lymphoblastic leukemia (ALL) and non-Hodgkin lymphoma. Mutations in this gene are associated with common variable immunodeficiency 3 (CVID3), characterized by impaired B cell differentiation and hypogammaglobulinemia. Owing to its B-cell-specific expression, CD19 has become a pivotal target for immunotherapy. For example, anti-CD19 CAR-T cell therapy (e.g., Tisagenlecleucel) has shown remarkable efficacy in refractory or relapsed ALL ^[5]. Recent studies have also explored CD19-targeted bispecific antibodies (e.g., blinatumomab) to enhance tumor cell clearance ^[6]. B6-hCD3/hCD19 mouse is a dual-gene humanized model generated by crossing B6-hCD3 mice (Catalog No.: C001325) with B6-hCD19 mice (Catalog No.: C001731). This strain is applicable for the development, validation, and preclinical evaluation of bispecific antibodies targeting human CD3/CD19, as well as for research on malignant tumors such as B-cell lymphoma and immunosuppressive therapies for autoimmune diseases. It serves as an ideal platform for the development of combination therapies.

Programmed cell death protein 1 (PDCD1/PD-1) is a member of the B7-CD28 costimulatory receptor family. It is an inhibitory receptor expressed on activated T cells and plays a role in regulating the function of effector T cells, including CD8+ T cells, and promoting the differentiation of CD4+ T cells into regulatory T cells. PD-1 is expressed in a variety of tumors and plays an important role in antitumor immunity. In addition, PD-1 is involved in the defense against autoimmune diseases and has inhibitory effects on antitumor and antimicrobial immunity ^[1]. Programmed cell death 1 ligand 1 (PD-L1), also known as cluster of differentiation 274 (CD274) or B7 homolog 1 (B7H1), is an immune inhibitory receptor ligand. PD-L1 is a type I transmembrane protein with immunoglobulin V-like (IgV) and C-like (IgC) structural domains and is expressed by hematopoietic and non-hematopoietic cells, including T cells, B cells, and various types of tumor cells ^[2]. PD-L1 can bind to the PD-1 on the surface of CD8+ T cells, inhibiting the activity of CD8+ T cells. This interaction can prevent the immune system from damaging normal tissues, but it can also be used by tumor cells to escape immune surveillance. Monoclonal antibodies that competitively bind to PD-L1 can relieve the immune function inhibition mediated by the binding of PD-1 and PD-L1. This can reactivate CD8+ T cells, triggering the human body's anti-tumor immune response ^[3]. Therefore, development of antibody drugs targeting PD-1 and PD-L1 is a hot area in tumor immunotherapy ^[3-5]. The Vascular Endothelial Growth Factor (VEGF) family is a group of particular endothelial growth factors intimately associated with angiogenesis. These factors promote increased vascular permeability, extracellular matrix degeneration, vascular endothelial cell migration and proliferation, and are capable of stimulating angiogenesis and increasing the permeability of existing vessels. As such, they play a pivotal role in normal vascular development and wound healing. The VEGF family comprises VEGFA, VEGFB, VEGFC, VEGFD, VEGFE, and PLGF ^[6]. Of these, VEGFA is the most commonly targeted in research related to neovascular ophthalmic diseases due to its crucial role in the proliferation, migration, and formation of endothelial cell microvessels ^[7]. Overexpression of VEGFA in the eye can result in abnormal vascular growth and leakage, leading to various ophthalmic diseases such as Age-Related Macular Degeneration (AMD), Diabetic Retinopathy (DR), and corneal neovascularization ^[7-8]. The progression of solid tumors depends on vascularization and angiogenesis within malignant tissues, with VEGFA playing a crucial role among various pro-angiogenic factors. The VEGFA gene is upregulated in many known tumors, correlating with tumor staging and progression. Blocking VEGFA may lead to vascular network regression, thereby inhibiting tumor growth ^[9]. Thus, VEGFA is an important target for anti-angiogenic cancer therapies. B6-hPD-1/hPD-L1/hVEGFA mouse is a triple-gene humanized model generated by crossing B6-hPD-1/hPD-L1 mice (Catalog No.: I001202) with B6-hVEGFA mice (Catalog No.: C001555). This model serves as a valuable tool for research on cancer immunotherapy and can also be used for the screening, development, and preclinical evaluation of PD-1/PD-L1/VEGFA-targeted drugs.