CD19 Chimeric Antigen Receptor (CAR): A Comprehensive Guide and Our Service & Product Introduction

CD19 Chimeric Antigen Receptor (CAR) technology has revolutionized the field of immunotherapy, especially in the treatment of B-cell malignancies. As a professional provider of gene editing tools and custom services, our company is committed to supporting global researchers and pharmaceutical enterprises in CD19 CAR-related basic research by offering high-quality CD19 CAR expression plasmid vectors and personalized vector construction services.

Our CD19 CAR Expression Plasmid Vector Products and Custom Services

As a professional provider of gene editing tools and custom services, our company has long been committed to the research and development, production, and sales of CD19 CAR-related products. We provide a full range of CD19 CAR expression plasmid vector products covering different generations, as well as personalized plasmid vector construction custom services, to meet the diverse needs of researchers in basic research and other stages. Our products have the advantages of high quality, high efficiency, and good stability, and our custom services have the characteristics of professionalism, rapidity, and flexibility, which have been widely recognized by global researchers.

1) Comprehensive Coverage of Generations: We provide multiple generations of CD19 CAR expression plasmid vectors, including: ① First-generation (scFv-CD3ζ); ② Second-generation (scFv-CD28-CD3ζ, scFv-4-1BB-CD3ζ); ③ Third-generation (scFv-CD28-4-1BB-CD3ζ, scFv-CD28-OX40-CD3ζ, scFv-CD28-CD27-CD3ζ); ④ Fourth-generation (scFv-CD28-4-1BB-CD3ζ-IL-12, scFv-CD28-4-1BB-CD3ζ-IL-15). Customers can choose the appropriate generation of vector according to their research needs.

2) Optimized Promoter Selection: We use high-efficiency promoters to ensure high-level expression of CD19 CAR in immune cells (T cells, NK cells). The optional promoters include CMV promoter (strong constitutive expression, suitable for most cell types), EF1α promoter (stable expression, low cell type dependence, not affected by cell cycle), and inducible promoters (such as Tet-on system, which can regulate the expression of CD19 CAR in a time-specific and dose-specific manner, improving the safety of research). Customers can choose the appropriate promoter according to the cell type and research needs.

3) Diversified Fluorescent Markers: To facilitate the detection and sorting of CAR-positive cells, our vectors are integrated with diversified fluorescent marker genes, including EGFP (green fluorescent protein, the most commonly used, high brightness, low toxicity), mCherry (red fluorescent protein, good stability, no overlap with EGFP fluorescence), mKate2 (far-red fluorescent protein, low background, suitable for in vivo imaging), and Luciferase (luciferase, which can be used for in vivo bioluminescence imaging to track the distribution and survival of CAR-positive cells in vivo). Customers can choose the appropriate fluorescent marker according to the detection method (such as flow cytometry, fluorescence microscopy, in vivo imaging).

Introduction of CD19

CD19, also known as B-lymphocyte antigen CD19, is encoded by the CD19 gene located on human chromosome 16p11.2. The CD19 gene spans approximately 15 kb and consists of 15 exons, which encode a transmembrane glycoprotein belonging to the immunoglobulin superfamily. The NCBI Gene ID of human CD19 is 930, and its mRNA sequence (e.g., NM_001178098.3) and amino acid sequence (e.g., NP_001171569.1) have been fully annotated, providing a solid foundation for gene cloning, vector construction, and functional research.

CD19 is a type I transmembrane glycoprotein with a molecular weight of approximately 90-95 kDa, composed of 430 amino acids (in humans). Its structure can be divided into three functional domains: the extracellular region, the transmembrane region, and the intracellular region.
1) Extracellular Region: Contains two C2-type immunoglobulin-like domains, which are responsible for ligand binding and participating in the formation of multimolecular complexes with other proteins on the B-cell surface.
2) Transmembrane Region: A hydrophobic α-helix structure that anchors CD19 to the B-cell membrane and mediates the connection between the extracellular and intracellular regions.
3) Intracellular Region: A relatively long sequence containing multiple conserved tyrosine phosphorylation sites, which can recruit downstream signaling molecules (such as PI3K, Syk) to initiate intracellular signaling cascades.

CD19 functions as a coreceptor for the B-cell antigen receptor (BCR) complex and plays a crucial role in B-cell development, activation, proliferation, differentiation, and immune tolerance regulation. Specifically, CD19 forms a multimolecular complex with CD21 (complement receptor 2), CD81 (TAPA-1), and Leu-13 on the B-cell surface. When BCR recognizes antigens, this complex can simultaneously bind to complement fragment C3d-coated antigens, synergistically amplifying the BCR signaling by 10-1000 times, thereby significantly reducing the threshold for B-cell activation. Additionally, CD19 is involved in the generation of memory B cells and the maintenance of humoral immune homeostasis; its deficiency can lead to impaired B-cell maturation and antibody production, resulting in immune deficiency disorders.

CD19 has a highly specific expression pattern, mainly restricted to the B-cell lineage. It is stably expressed from pro-B cells to mature B cells throughout the B-cell development process but is lost when B cells terminally differentiate into plasma cells. In addition to B cells, CD19 is also weakly expressed on follicular dendritic cells and peritoneal mast cells (co-localized with CD21/CD35), but not expressed on T cells, natural killer (NK) cells, monocytes, granulocytes, or other non-B cells. This "B-cell-specific" expression pattern makes CD19 an ideal target for targeted therapy of B-cell-related diseases, avoiding off-target effects on other normal cells.

Abnormal expression or dysfunction of CD19 is closely associated with a variety of diseases, mainly including B-cell malignancies and autoimmune diseases, which also lays the foundation for CD19 as a core therapeutic target.
1) B-cell Malignancies: Almost all B-cell-derived hematological tumors highly express CD19, including acute B-lymphoblastic leukemia (B-ALL, >90% of patients), diffuse large B-cell lymphoma (DLBCL), chronic lymphocytic leukemia (CLL), follicular lymphoma (FL), mantle cell lymphoma (MCL), etc. CD19 is not only a key marker for the diagnosis and immunophenotyping of these tumors but also a core target for immunotherapy (such as CAR-T cell therapy, antibody-drug conjugates).
2) Autoimmune Diseases: Pathologically activated autoreactive B cells are the core driving factors of many autoimmune diseases. In diseases such as systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and multiple sclerosis (MS), targeted clearance of autoreactive B cells by targeting CD19 can effectively alleviate disease symptoms. For example, CD19 CAR-T therapy has shown potential for deep remission in refractory SLE.
3) Immunodeficiency Diseases: Rare congenital immunodeficiency diseases associated with CD19 gene mutations are characterized by impaired antibody production and increased susceptibility to infections, which are caused by abnormal B-cell development and activation due to CD19 dysfunction.

Introduction of CD19 CAR

CD19 CAR is the most mature and widely studied type of CAR, which targets the CD19 antigen specifically expressed on B cells. It is the core technology of CAR-T cell therapy for B-cell malignancies, and has achieved remarkable results in clinical application. It is also the focus of current basic research and clinical transformation. Since the first clinical trial of CD19 CAR-T cells in 2010, CD19 CAR technology has developed rapidly, and a large number of preclinical and clinical research results have been achieved, covering B-cell malignancies, autoimmune diseases, and other fields.

In basic research, the optimization of CD19 CAR structure has made continuous progress, such as the development of humanized scFv (reducing immunogenicity), the optimization of hinge region and transmembrane region (improving CAR stability and expression level), and the modification of intracellular signaling domain (enhancing CAR-T cell function and reducing exhaustion). In addition, the development of CD19 CAR-NK cells, CD19 CAR-macrophages, and other novel CAR-engineered immune cells has overcome the limitations of CAR-T cells (such as graft-versus-host disease, GVHD) and expanded the application scope of CD19 CAR technology. For example, a humanized single-chain antibody targeting human CD19 antigen was developed based on the murine FMC63 antibody, and a CD19 CAR constructed based on this antibody showed high specificity and affinity for CD19 antigen, and strong killing effect on CD19-positive tumor cells.

B-cell Malignancies
CD19 CAR-T cell therapy has become the first-line or second-line treatment for refractory/relapsed B-cell malignancies, with remarkable therapeutic effects. For example, in the treatment of relapsed/refractory acute B-lymphoblastic leukemia (B-ALL), the overall remission rate (ORR) of CD19 CAR-T cell therapy can reach 80%-90%, and the event-free survival rate (EFS) and overall survival rate (OS) are significantly higher than those of traditional chemotherapy and hematopoietic stem cell transplantation. In a preclinical study of CD19 CAR-T cells for CD19-positive acute myeloid leukemia (AML), CD19 CAR-T cells showed potent cytotoxicity against CD19-positive AML cells in vitro (~60% target cell killing at 4 hours with a 2:1 E:T ratio) and significantly prolonged the survival time of tumor-bearing mice in vivo. In the treatment of relapsed/refractory diffuse large B-cell lymphoma (DLBCL), the ORR of CD19 CAR-T cell therapy is 50%-70%, and the complete remission rate (CR) is 30%-50%. For chronic lymphocytic leukemia (CLL), follicular lymphoma (FL), and other diseases, CD19 CAR-T cell therapy also shows good therapeutic potential, especially for patients who are refractory to traditional treatment.

Autoimmune Diseases
In recent years, CD19 CAR-T cell therapy has gradually expanded to the field of autoimmune diseases. By targeting and clearing autoreactive B cells, it has achieved good therapeutic effects in refractory systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), multiple sclerosis (MS), and other diseases. For example, in a clinical trial of CD19 CAR-T cell therapy for refractory SLE, most patients achieved deep remission, and some patients maintained remission for more than 3 years after stopping drugs, which was significantly better than that of traditional immunosuppressive therapy. As of May 2025, there were 164 clinical trials of CAR-T cell therapy for autoimmune diseases registered on ClinicalTrials.gov, of which nearly half targeted CD19, showing the broad application prospects of CD19 CAR in this field.

Marketed Drugs
At present, a number of CD19 CAR-T cell therapy drugs have been approved for marketing globally, all of which are second-generation CAR-T drugs, mainly used for the treatment of relapsed/refractory B-cell malignancies. The representative marketed drugs are as follows:
1) Tisagenlecleucel (trade name: Kymriah): Developed by Novartis, it was approved by the US FDA in 2017 for the treatment of relapsed/refractory pediatric and young adult B-ALL, and later approved for the treatment of relapsed/refractory DLBCL. It is a 4-1BB-based second-generation CD19 CAR-T drug, which has the characteristics of long survival time of CAR-T cells and strong long-term anti-tumor effect. It is the first CAR-T drug approved for marketing in the world, marking the entry of CAR-T therapy into the clinical application stage in an all-round way.
2) Axicabtagene ciloleucel (trade name: Yescarta): Developed by Kite Pharma (acquired by Gilead Sciences), it was approved by the US FDA in 2017 for the treatment of relapsed/refractory DLBCL and primary mediastinal large B-cell lymphoma (PMBCL). It is a CD28-based second-generation CD19 CAR-T drug, which has the characteristics of fast activation speed and strong short-term killing effect, and has achieved remarkable therapeutic effects in the treatment of aggressive B-cell lymphoma.
3) Brexucabtagene autoleucel (trade name: Tecartus): Developed by Kite Pharma, it was approved by the US FDA in 2020 for the treatment of relapsed/refractory mantle cell lymphoma (MCL) and relapsed/refractory B-ALL. It is a CD28-based second-generation CD19 CAR-T drug, which has high killing efficiency against MCL and B-ALL cells, and can improve the survival rate of patients with refractory diseases.
4) Lisocabtagene maraleucel (trade name: Breyanzi): Developed by Juno Therapeutics (acquired by Bristol-Myers Squibb), it was approved by the US FDA in 2021 for the treatment of relapsed/refractory DLBCL. It is a 4-1BB-based second-generation CD19 CAR-T drug, which has low immune-related adverse reactions and good safety while ensuring therapeutic effect. In addition, a number of CD19 CAR-T drugs are in the late clinical trial stage (Phase II/III), covering more B-cell malignancies and autoimmune diseases, which will further expand the application scope of CD19 CAR technology and benefit more patients.

Research Hotspots
With the in-depth research and clinical application of CD19 CAR, the current research hotspots mainly focus on optimizing CAR structure, improving therapeutic effect, reducing adverse reactions, expanding application scope, and simplifying treatment procedures, specifically including the following aspects:
1) Optimization of CD19 CAR Structure: Focus on the development of humanized/mouse-human chimeric scFv to reduce the immunogenicity of CAR and avoid the generation of anti-CAR antibodies (which lead to CAR-T cell clearance and treatment failure); optimize the hinge region and transmembrane region to improve the stability and surface expression level of CAR; modify the intracellular signaling domain to enhance the proliferation, survival ability, and anti-exhaustion ability of CAR-T cells. For example, the combination of different costimulatory domains (such as CD28+4-1BB+OX40) and the addition of immune checkpoint inhibitors (such as PD-1/PD-L1 blockers) to the CAR structure can further improve the therapeutic effect.
2) Development of Universal CD19 CAR-T Cells (Off-the-Shelf CAR-T): Traditional autologous CAR-T cells have the disadvantages of long preparation cycle, high cost, and poor quality consistency (affected by the patient's own immune status). The research and development of universal CAR-T cells (using healthy donor T cells, modifying TCR and CD52 genes to avoid GVHD and immune rejection) has become a hot spot. It can be prepared in advance, shorten the treatment cycle, reduce the cost, and improve the quality consistency, which is expected to make CAR-T therapy more accessible. At present, a number of universal CD19 CAR-T drugs are in the early clinical trial stage, and have shown good safety and therapeutic potential.
3) Combination Therapy of CD19 CAR-T Cells: To improve the therapeutic effect and reduce tumor recurrence, CD19 CAR-T cell therapy is often combined with other therapies, such as chemotherapy (preconditioning chemotherapy to reduce tumor load and create a suitable immune microenvironment), targeted therapy (BCL-2 inhibitors, PI3K inhibitors), immune checkpoint inhibitors (PD-1/PD-L1 antibodies), and radiotherapy. Preclinical and clinical studies have shown that combination therapy can significantly improve the ORR and CR of patients, and prolong the survival time. For example, the combination of CD19 CAR-T cells and BCL-2 inhibitors can enhance the killing effect on refractory B-ALL cells.
4) Application Expansion of CD19 CAR: On the basis of B-cell malignancies, further expand the application scope of CD19 CAR to autoimmune diseases (such as SLE, RA, MS), immune deficiency diseases, and even solid tumors (such as CD19-positive ovarian cancer, breast cancer). In the field of autoimmune diseases, CD19 CAR-T cell therapy has shown good potential, and more clinical trials are being carried out to verify its long-term safety and efficacy. In addition, the development of CD19 CAR-NK cells, CD19 CAR-macrophages, and other novel CAR-engineered immune cells is also a research hotspot, which can overcome the limitations of CAR-T cells and expand the application scenarios.
5) In Vivo Induction of CD19 CAR-T Cells: The traditional in vitro CAR-T cell preparation process is complex, time-consuming, labor-intensive, and costly, which limits its wide application. The development of in vivo induction technology of CD19 CAR-T cells (such as delivering CD19 CAR genes to T cells in vivo through nanoparticles, lentivirus, adeno-associated virus (AAV), etc.) has become a new research hotspot. This technology can simplify the preparation process, reduce the cost, and reduce systemic adverse reactions (such as CRS, ICANS). Preclinical studies have shown that in vivo induced CD19 CAR-T cells have anti-tumor effects comparable to those of traditional in vitro prepared CAR-T cells, and have good safety. For example, nanoparticles carrying CD19-specific CAR genes can specifically edit T cells in vivo and achieve significant anti-tumor effects without causing systemic toxicity. The combination of gene editing tools (such as CRISPR/Cas9) and in vivo CAR delivery technology is also a research focus, which is expected to accelerate the clinical application of in vivo induced CD19 CAR-T cells.
6) Safety Improvement of CD19 CAR-T Cells: The addition of safety switches (such as suicide genes, inducible caspase-9) to the CD19 CAR structure can quickly eliminate CAR-T cells when severe adverse reactions occur, improving the safety of treatment. In addition, optimizing the cytokine secretion level of CAR-T cells to reduce the risk of CRS and neurotoxicity is also a research hotspot. For example, the use of inducible cytokine expression systems can control the secretion of cytokines in a target antigen-dependent manner, reducing non-specific cytokine release and adverse reactions.

Research Difficulties and Challenges

Although CD19 CAR technology has achieved remarkable results, there are still many difficulties and challenges in basic research, clinical application, and industrialization, which restrict its further development and popularization:
1) Tumor Antigen Escape: This is the most important challenge faced by CD19 CAR-T cell therapy. Some patients will have tumor recurrence after treatment, mainly because tumor cells downregulate or lose CD19 expression (CD19-negative escape) through gene mutation, alternative splicing, or epigenetic modification, making CD19 CAR-T cells unable to recognize and kill tumor cells. In addition, tumor cells can also escape immune killing by upregulating immune checkpoint molecules (such as PD-L1) or secreting immunosuppressive cytokines (such as TGF-β). How to overcome tumor antigen escape and reduce recurrence rate is a key difficulty in current research. The development of dual-target CAR (such as CD19/CD20, CD19/CD22, CD19/CD37) and multi-target CAR is one of the important strategies to solve this problem.
2) Immune-Related Adverse Reactions: CD19 CAR-T cell therapy can cause a series of immune-related adverse reactions, mainly including cytokine release syndrome (CRS), immune effector cell-associated neurotoxicity syndrome (ICANS), GVHD (for allogeneic CAR-T), and long-term B-cell depletion (leading to hypogammaglobulinemia). Among them, severe CRS and ICANS can even threaten the patient's life. At present, the mechanism of these adverse reactions is not fully clear, and there is a lack of effective prevention and treatment methods. How to balance the therapeutic effect and safety, and reduce the incidence and severity of adverse reactions is another important challenge. The optimization of CAR structure (such as the selection of costimulatory domains), the regulation of cytokine secretion, and the development of safety switches are important ways to solve this problem.
3) High Cost and Low Accessibility: Traditional autologous CD19 CAR-T cell therapy has high production cost (each treatment costs hundreds of thousands of US dollars), long preparation cycle (2-4 weeks), and high technical threshold, which makes most patients unable to afford it and limits its popularization in developing countries and regions. Although universal CAR-T cells and in vivo induced CAR-T cells are expected to reduce the cost and shorten the preparation cycle, there are still many technical problems to be solved (such as immune rejection, low in vivo induction efficiency). How to reduce the production cost, simplify the production process, and improve the accessibility of CAR-T therapy is a major challenge in industrialization.
4) T-cell Exhaustion: Long-term activation of CD19 CAR-T cells in vivo will lead to T-cell exhaustion, which is characterized by decreased proliferation ability, reduced killing efficiency, increased expression of exhaustion-related molecules (such as PD-1, TIM-3, LAG-3), and shortened survival time, resulting in reduced long-term anti-tumor effect and increased tumor recurrence rate. The mechanism of T-cell exhaustion is complex, related to the tumor microenvironment, CAR structure, and cytokine secretion. How to inhibit T-cell exhaustion and maintain the long-term function of CAR-T cells is a key difficulty in basic research. The modification of intracellular signaling domains, the combination of immune checkpoint inhibitors, and the optimization of the tumor microenvironment are important strategies to solve this problem.
5) Application Limitations in Autoimmune Diseases: Although CD19 CAR-T cell therapy has shown good potential in autoimmune diseases, there are still many challenges, such as the lack of unified treatment standards (such as the dosage of CAR-T cells, preconditioning chemotherapy regimen), the unclear long-term safety (such as the risk of infection and secondary tumors after long-term B-cell depletion), and the difficulty in evaluating the treatment effect. In addition, autoimmune diseases are chronic diseases, and the risk-benefit ratio of lymphodepletion chemotherapy needs to be re-evaluated, and the fertility concerns of young patients have also become an obstacle to treatment. How to formulate personalized treatment plans and verify the long-term safety and efficacy is a key challenge in the expansion of CD19 CAR application in autoimmune diseases.
6) Technical Limitations of In Vivo Induction: Although in vivo induced CD19 CAR-T cells have broad prospects, there are still many technical limitations, such as the non-specificity of viral vectors (which may transduce non-T cells, leading to off-target effects), the low efficiency of in vivo gene delivery, and the potential risk of random insertion of viral vectors into chromosomes (which may cause gene mutation and secondary tumors). How to improve the specificity and efficiency of in vivo gene delivery, and reduce the safety risks of vectors is a key challenge in the research of in vivo induced CD19 CAR-T cells. The development of targeted delivery systems (such as T-cell-specific nanocarriers, dual-specific binders) and the combination of gene editing tools (such as CRISPR/Cas9) are important ways to solve this problem.

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