Interferons (IFNs) are potent cytokines that serve as a critical component of the body's first line of defense against viral infections, playing a key role in inflammation and immune control by directly inducing pathogen-inhibiting molecules that suppress viral replication ^[1]. Arthropod-borne viruses (arboviruses) like Dengue virus (DENV), Zika virus (ZIKV), and Yellow Fever virus (YFV) encode proteins that antagonize the IFN response, helping these viruses evade host immunity and maintain sufficient viral loads in the blood (viremia) to sustain the vector-host transmission. Arboviruses pose a significant public health threat, affecting around 3.9 billion people in tropical and subtropical regions. However, most preclinical studies suggest that arboviruses cannot inhibit IFN responses in mice, rendering immunocompetent mice resistant to infection, with low viral loads and limited circulation, thus limiting their use in infection research ^[2-3]. As a result, immunodeficient mouse models with defects in multiple IFN signaling pathways have become essential tools for studying arbovirus pathogenesis and vaccine development ^[2-4]. Studies have demonstrated that wild-type mice of strains like C57BL/6, CD-1, or 129 rarely exhibit clinical symptoms after infection with arboviruses such as ZIKV. However, the virus has been detected in the blood, ovaries, and spleen of ZIKV-infected 129 mice, suggesting that this strain may be more susceptible to arboviruses ^[5-6]. Because the virus can persist in the bloodstream without causing disease or death, the 129 strain can be used to evaluate the teratogenic effects of such viruses. Furthermore, the 129 strain is commonly used in interferon signaling-deficient models related to other viral infections ^[7-8]. The IFNAR1 gene encodes a protein that is an essential component of the type I interferon (IFN) receptor, playing a critical role in the antiviral and immune responses. IFNAR1 is primarily expressed in immune cells, such as lymphocytes and dendritic cells, and various tissues, including the liver, brain, and skin. Defects in IFNAR1, whether due to mutations or regulatory abnormalities, can lead to severe diseases such as systemic lupus erythematosus, where excessive immune activation results in tissue damage, and certain cancers. Other diseases associated with IFNAR1 include hepatitis C, yellow fever, measles, papilloma, and viral infections. The A129 (Ifnar1 KO) mice on a 129 background are a type I (α/β) interferon receptor (Ifnar1) gene knockout model. The absence of the IFNAR1 protein in these mice leads to a lack of type I IFN receptor function, thereby reducing immune response and increasing susceptibility to viral infections. Homozygous A129 (Ifnar1 KO) mice are viable and fertile, but they show increased susceptibility to arbovirus infections.

Interferons (IFNs) are potent cytokines that serve as a critical component of the body's first line of defense against viral infections, playing a key role in inflammation and immune control by directly inducing pathogen-inhibiting molecules that suppress viral replication ^[1]. Arthropod-borne viruses (arboviruses) like Dengue virus (DENV), Zika virus (ZIKV), and Yellow Fever virus (YFV) encode proteins that antagonize the IFN response, helping these viruses evade host immunity and maintain sufficient viral loads in the blood (viremia) to sustain the vector-host transmission. Arboviruses pose a significant public health threat, affecting around 3.9 billion people in tropical and subtropical regions. However, most preclinical studies suggest that arboviruses cannot inhibit IFN responses in mice, rendering immunocompetent mice resistant to infection, with low viral loads and limited circulation, thus limiting their use in infection research ^[2-3]. As a result, immunodeficient mouse models with defects in multiple IFN signaling pathways have become essential tools for studying arbovirus pathogenesis and vaccine development ^[2-4]. Studies have demonstrated that wild-type mice of strains like C57BL/6, CD-1, or 129 rarely exhibit clinical symptoms after infection with arboviruses such as ZIKV. However, the virus has been detected in the blood, ovaries, and spleen of ZIKV-infected 129 mice, suggesting that this strain may be more susceptible to arboviruses ^[5-6]. Because the virus can persist in the bloodstream without causing disease or death, the 129 strain can be used to evaluate the teratogenic effects of such viruses. Furthermore, the 129 strain is commonly used in interferon signaling-deficient models related to other viral infections ^[7-8]. The IFNAR1 gene encodes a key component of the type I IFN receptor, while the IFNGR1 gene encodes the ligand-binding chain (α) of the type II (γ) IFN receptor. AG129 mice, which are knockout models for both the type I (α/β) IFN receptor (Ifnar1) and the type II (γ) IFN receptor (Ifngr1), lack functional IFNAR1 and IFNGR1 proteins, resulting in deficiencies in α/β/γ interferon receptor signaling and heightened susceptibility to viral infections. Homozygous AG129 mice are viable and fertile, and exhibit increased sensitivity to arboviral infections, generating viremia similar to that seen in humans. Compared to IFNα/β/γR KO mice on the C57BL/6 background, the 129-background AG129 mice exhibit more pronounced neurological symptoms after infection ^[6,9].

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 ^[1]. 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 ^[2]. Recent studies have also explored CD19-targeted bispecific antibodies (e.g., blinatumomab) to enhance tumor cell clearance ^[3]. B6-hCD19 mice are a humanized model generated by replacing the mouse endogenous Cd19 gene sequence from the ATG start codon to part of intron 4 with the corresponding human CD19 gene sequence using gene editing technology. This model is applicable for studying B cell development and function, as well as therapeutic research on autoimmune diseases such as systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA), and B cell malignancies. It is an ideal research platform for preclinical efficacy evaluation of anti-human CD19 CAR-T cell therapy, and the development of bispecific antibodies and combination therapies.

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]. B6-hPCSK9 mice are a humanized model generated by gene editing technology to replace the mouse Pcsk9 gene with the human PCSK9 gene sequence. These mice express human PCSK9 protein and can be used for research on various metabolic diseases, neurodegenerative diseases, tumor development, autoimmune disease mechanisms, and for the preclinical pharmacological evaluation of PCSK9-targeted drugs. In addition, Cyagen has developed a similar model, the B6-hPCSK9(CDS) mouse (PCSK9 coding sequence humanized model, Catalog Number: C001593). Compared to the B6-hPCSK9 mouse model, the B6-hPCSK9(CDS) mouse expresses higher levels of human PCSK9 and exhibits LDLR protein expression closer to physiological levels. It is recommended to choose the appropriate model based on the type of drug or research direction.

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).

The TNFRSF13B gene encodes the transmembrane activator and CAML interactor (TACI), a receptor belonging to the tumor necrosis factor receptor superfamily, predominantly expressed on B lymphocytes. TACI plays a critical role in humoral immunity by recognizing the TNF ligands B cell-activating factor (BAFF) and a proliferation-inducing ligand (APRIL) ^[1]. Upon ligand binding, TACI modulates intracellular signaling pathways, including NFAT, AP1, and NF-κB, which are essential for B cell survival, maturation into plasma cells, and the production of immunoglobulins ^[2]. Notably, TNFRSF13B is highly polymorphic, and specific genetic variants are strongly associated with the pathogenesis of common variable immunodeficiency (CVID), a primary immunodeficiency characterized by hypogammaglobulinemia and increased susceptibility to infection ^[3]. While the precise mechanisms by which these variants contribute to disease are still under investigation, they often result in impaired TACI function, disrupting normal B cell development and antibody responses ^[4]. Further research into the regulation and function of TACI is crucial for understanding the complex etiology of CVID and for developing targeted therapeutic strategies for this and potentially other immune-related disorders. The B6-hTNFRSF13B mouse is a humanized model constructed by replacing the exon 2 plus partial intron 2 of the mouse Tnfrsf13b gene in situ with the "Kozak-TNFRSF13B chimeric CDS-3'UTR of mouse Tnfrsf13b-WPRE-BGH pA" cassette. The B6-hTNFRSF13B mice can be used for studies on common variable immunodeficiency (CVID), and pathogenesis of immune-related diseases, as well as for TNFRSF13B-targeted drug development.

The CLEC4C gene, also known as BDCA-2 or CD303, encodes a type II transmembrane C-type lectin receptor predominantly expressed by plasmacytoid dendritic cells (pDCs) ^[1]. This receptor plays a critical role in pDC biology and serves as a key marker for this cell type ^[2]. The CLEC4C protein, featuring a carbohydrate recognition domain, is implicated in the capture and subsequent processing of antigens, potentially through the recognition of specific glycans and immunoglobulin G ^[1]. Functionally, CLEC4C acts as a signaling receptor within pDCs, and its engagement can negatively regulate the production of type I interferons, thereby modulating immune responses ^[2]. Notably, dysregulation of CLEC4C expression and pDC function has been associated with the pathogenesis of autoimmune disorders, including systemic lupus erythematosus (SLE), as well as in the context of certain hematological malignancies ^[3]. Litifilimab is a monoclonal antibody that targets CLEC4C and is under investigation for the treatment of SLE and other interferonopathies ^[4]. CLEC4C is a human gene, while Clec4b1 is its orthologous gene in mice. The B6-hCLEC4C mouse is a humanized model constructed by replacing the mouse Clec4b1 endogenous extracellular domain with the human CLEC4C extracellular domain. This model can be used to study the pathological mechanisms and therapeutic methods of autoimmune disorders and hematological malignancies, as well as the screening and development of CLEC4C-targeted drugs, and preclinical efficacy and safety evaluations.

The gene TNFRSF13C encodes the B cell-activating factor receptor (BAFF-R), also known as BLyS receptor 3 (BR3) or CD268. As a member of the tumor necrosis factor receptor superfamily (TNFRSF), BAFF-R functions as a crucial type III transmembrane signaling protein on lymphocytes. Its expression is predominantly observed on the surface of B cells throughout various stages of their development, from transitional to mature naive and memory populations, underscoring its vital role in peripheral B cell homeostasis ^[1]. BAFF-R serves as the primary receptor for the cytokine BAFF (TNFSF13B), and their interaction delivers essential survival and maturation signals to B cells, mediated through downstream pathways including the activation of NF-κB and PI3K. Genetic alterations in TNFRSF13C, including point mutations and deletions, or dysregulation of the BAFF-BAFF-R axis, are increasingly recognized for their contribution to immune pathology ^[2]. Such aberrations are associated with primary immunodeficiencies like common variable immunodeficiency (CVID), characterized by profound defects in antibody production and recurrent infections, as well as a range of autoimmune diseases such as systemic lupus erythematosus (SLE) and Sjögren's syndrome, and certain B cell malignancies ^[2-3]. The critical, non-redundant function of BAFF-R in B cell biology highlights its significance as a key node in adaptive immunity and positions the BAFF-BAFF-R pathway as a compelling target for therapeutic intervention in a spectrum of immune-mediated disorders. The B6-hBAFFR (hTNFRSF13C) mouse is a humanized model constructed by replacing the sequence of the mouse Tnfrsf13c endogenous extracellular domain in situ with the corresponding extracellular domain from the human TNFRSF13C. The B6-hBAFFR (hTNFRSF13C) mice can be used for the study of the pathogenesis of immune-mediated disorders such as common variable immunodeficiency (CVID), systemic lupus erythematosus (SLE), and Sjögren's syndrome, and certain B cell malignancies, as well as for TNFRSF13C-targeted drug development.

Interleukin-13, encoded by the IL13 gene, is a key type 2 immune response cytokine, predominantly expressed by activated Th2 helper T cells, type 2 innate lymphoid cells (ILC2s), and mast cells, and central to type 2 immune responses elicited by allergens or other stimuli ^[1]. The IL-13 protein, a ~13 kDa molecule with a four-helix bundle structure, mediates its biological effects by binding to the cell surface receptor IL-13Rα1 and recruiting the IL-4Rα chain to form a functional receptor complex, thereby activating the downstream JAK/STAT6 signaling pathway ^[2]. Key functions of IL-13 include promoting B cell maturation and plasma cell differentiation, inducing IgE isotype switching, and suppressing the pro-inflammatory activity of macrophages, leading to reduced production of pro-inflammatory cytokines and chemokines ^[3]. Furthermore, IL-13 induces goblet cell hyperplasia, promotes mucus secretion, and contributes to airway remodeling and fibrosis ^[4]. Numerous studies have established the critical role of IL-13 in the pathogenesis of various diseases, including asthma, allergic rhinitis, atopic dermatitis, and eosinophilic esophagitis ^[1-4]. Consequently, targeting IL-13 and its signaling pathways has become a significant therapeutic strategy for these conditions; for example, the monoclonal antibody Dupilumab, which simultaneously blocks IL-4 and IL-13 signaling, has demonstrated substantial efficacy in treating diverse type 2 inflammation-related diseases ^[5]. Thus, IL-13 represents a promising therapeutic target for allergic and inflammatory disorders. The IL23A gene encodes the p19 subunit, a component of interleukin-23 (IL-23), which forms a heterodimer with the p40 subunit (encoded by IL12B) to generate the functional IL-23 cytokine. Primarily expressed by activated dendritic cells, macrophages, and monocytes, IL-23 signals through the IL-23 receptor (IL-23R) complex, activating the JAK-STAT pathway to promote Th17 cell differentiation and maintain IL-17 production. This process drives inflammatory responses and mucosal immunity against extracellular pathogens ^[6-7]. Genetic polymorphisms within IL23A are strongly associated with autoimmune and inflammatory diseases, including psoriasis, Crohn's disease, and inflammatory bowel disease, due to dysregulated Th17 activity and chronic inflammation ^[6-7]. Monoclonal antibodies targeting IL-23, such as risankizumab and guselkumab, selectively block the p19 subunit, demonstrating therapeutic efficacy in psoriasis and inflammatory bowel diseases by suppressing pathogenic IL-17/Th17 pathways ^[8]. While IL-23 plays a role in protective immunity, its overactivation contributes to tissue damage in autoimmune settings, highlighting its dual function in immune regulation and disease pathogenesis ^[6-9]. B6-hIL13/hIL23A mice are humanized models generated by crossing B6-hIL13 mice (Product No.: C001634) with B6-hIL23A mice (Product No.: C001618). These mice are suitable for studying the pathological mechanisms and therapeutic strategies of allergic and inflammatory diseases, immune-related disorders, and cancer, as well as for the screening, development, and preclinical evaluation of IL13/IL23A-targeted drugs.

Thymic stromal lymphopoietin (TSLP), an interleukin-7 (IL-7) family cytokine, is encoded by the TSLP gene and is predominantly produced by epithelial cells. Its expression is notably upregulated by environmental cues, including allergens and proteases, positioning it as a sentinel at the interface of environmental exposure and immune activation ^[1-2]. Secreted by a range of cell types, such as epithelial cells, keratinocytes, mast cells, and dendritic cells, TSLP is critical in the initiation of immune responses, primarily through the activation of dendritic cells and subsequent polarization of T helper type 2 (Th2) cell differentiation. This process has broad implications for diverse immune cell populations and B cell functions relevant to allergic inflammation ^[2]. Transcriptional regulation of TSLP gene expression is tightly controlled by factors including NF-κB and AP-1, with genetic polymorphisms within the TSLP locus being strongly implicated in asthma susceptibility ^[1-3]. Dysregulated TSLP signaling is now recognized as a pivotal factor in the pathogenesis of atopic disorders, encompassing conditions such as atopic dermatitis, asthma, allergic rhinitis, and eosinophilic esophagitis ^[1-4]. For example, tezepelumab, a monoclonal antibody that blocks the TSLP signaling pathway, has demonstrated significant efficacy in clinical trials for patients with severe asthma, reducing acute exacerbations and improving lung function ^[4]. Consequently, TSLP is under intense investigation as a therapeutic target, with current strategies focusing on disrupting its signaling pathways to modulate allergic and inflammatory diseases ^[5]. The B6-hTSLP mouse is a humanized model constructed using gene editing technology, where the mouse Tslp endogenous domain was replaced with the human TSLP domain . The murine signal peptide was preserved. This model can be used for studying the pathological mechanisms and therapeutic approaches of allergic and inflammatory diseases and for the development of TSLP-targeted drugs.