CRISPR-Cas9 RNP editing of primary immune cells
Materials Required
Principle
CRISPR-Cas9 RNP editing uses preassembled Cas9 protein and guide RNA to direct sequence-specific DNA cleavage at a genomic target, after which cellular DNA repair generates insertions/deletions for knockout or uses an added donor template for knock-in[1][2]. In primary immune cells, published protocols deliver Cas9 RNPs mainly by electroporation or nucleofection because these methods can introduce protein-RNA complexes into difficult-to-transfect T cells, B cells, NK cells, monocytes, myeloid cells, and innate lymphoid cells without viral Cas9 expression[3][4][5][6][7][8][9][10][11].
MCE has not independently verified the accuracy of these methods. They are for reference only.
Experimental Materials
• Use purified primary immune cells appropriate to the study question, such as human CD4+ T cells, resting human B cells, human NK cells, CD14+ monocytes, murine myeloid cells, or murine innate lymphocytes, because these are the cell types directly tested in the cited RNP-editing studies[3][6][8][9][10][11].
• Use recombinant Cas9 protein and synthetic sgRNA or crRNA:tracrRNA to assemble RNPs before delivery; chemically modified or synthetic guide RNAs are preferred when supported by the target-cell protocol, and in vitro-transcribed guide RNAs should be avoided for immune-sensitive workflows because they can trigger a RIG-I-dependent type I interferon response[3][4][8][10][12].
• Use cell-type-specific culture media, cytokines, activation reagents, or feeder systems only when they match the published protocol: T-cell studies used activated or non-TCR-stimulated T-cell workflows, B-cell studies used EBV infection or CD40 ligand feeder culture after nucleofection, NK-cell studies used expansion before RNP/AAV editing, and monocyte/myeloid studies edited purified monocytes or myeloid cells by nucleofection[3][4][6][8][9][10][11].
• Use flow-cytometry antibodies against the edited protein when the target encodes a surface or intracellular protein, because multiple studies quantified knockout by loss of target protein expression after RNP editing[4][6][8][9][10][11].
• Use PCR amplicon sequencing, Sanger sequencing with indel analysis, or related amplicon-based assays to measure editing at the DNA level, because these readouts were used to quantify indels or confirm genome modification in primary immune-cell RNP studies[3][6][8][9][10][11].
• Use an electroporation or nucleofection device compatible with primary immune cells, because the cited protocols delivered Cas9 RNPs by electroporation/nucleofection rather than lipid transfection or viral Cas9 delivery[3][4][6][8][9][10][11].
• Use a flow cytometer for protein-loss readout and cell-viability assessment, and use a thermocycler plus Sanger or next-generation sequencing access for genomic editing analysis[4][6][8][9][10][11].
• Use recombinant Cas9 protein and synthetic sgRNA or crRNA:tracrRNA to assemble RNPs before delivery; chemically modified or synthetic guide RNAs are preferred when supported by the target-cell protocol, and in vitro-transcribed guide RNAs should be avoided for immune-sensitive workflows because they can trigger a RIG-I-dependent type I interferon response[3][4][8][10][12].
• Use cell-type-specific culture media, cytokines, activation reagents, or feeder systems only when they match the published protocol: T-cell studies used activated or non-TCR-stimulated T-cell workflows, B-cell studies used EBV infection or CD40 ligand feeder culture after nucleofection, NK-cell studies used expansion before RNP/AAV editing, and monocyte/myeloid studies edited purified monocytes or myeloid cells by nucleofection[3][4][6][8][9][10][11].
• Use flow-cytometry antibodies against the edited protein when the target encodes a surface or intracellular protein, because multiple studies quantified knockout by loss of target protein expression after RNP editing[4][6][8][9][10][11].
• Use PCR amplicon sequencing, Sanger sequencing with indel analysis, or related amplicon-based assays to measure editing at the DNA level, because these readouts were used to quantify indels or confirm genome modification in primary immune-cell RNP studies[3][6][8][9][10][11].
• Use an electroporation or nucleofection device compatible with primary immune cells, because the cited protocols delivered Cas9 RNPs by electroporation/nucleofection rather than lipid transfection or viral Cas9 delivery[3][4][6][8][9][10][11].
• Use a flow cytometer for protein-loss readout and cell-viability assessment, and use a thermocycler plus Sanger or next-generation sequencing access for genomic editing analysis[4][6][8][9][10][11].
Experimental Procedure
• Select the immune-cell type, target gene, and readout before beginning; surface proteins such as CD46, TCR-related targets, and myeloid or innate immune targets are useful positive technical examples because protein loss can be measured directly by flow cytometry[3][4][6][8][9][10][11].
• Design guide RNAs against the target locus and include a non-targeting or safe-harbor/control guide when possible; assemble Cas9 and guide RNA as RNP immediately before delivery, following the cell-type-specific RNP format used in the selected source protocol[3][4][6][8][9][10][11].
• Prepare cells according to the matching immune-cell protocol: activate or culture T cells as required by the chosen T-cell method, maintain resting B cells before nucleofection when following the B-cell study, expand NK cells before site-specific insertion workflows, or purify CD14+ monocytes before monocyte editing[3][4][8][9][10][11].
• Deliver the preassembled Cas9 RNP into primary immune cells by electroporation or nucleofection using the program and buffer conditions validated for the specific cell type; because instrument programs and buffer formulations differ across studies, use only the exact settings reported for the chosen cell type rather than transferring settings between T cells, B cells, NK cells, monocytes, and ILC/myeloid cells[3][4][6][8][9][10][11].
• For knockout experiments, culture edited cells after RNP delivery until protein loss or indel formation can be measured; reported studies analyzed editing by flow cytometry and/or DNA amplicon analysis after recovery, expansion, differentiation, infection, or stimulation steps appropriate to the immune-cell type[4][6][8][9][10][11].
• For knock-in experiments, provide a donor repair template only in workflows where donor delivery was tested, such as Cas9 RNP with HDR donor in primary human T cells, non-viral donor targeting in T cells, modified repair templates with Cas9 RNP, or Cas9 RNP plus AAV in primary NK cells[3][5][7][9].
• Do not add unsupported enhancers or handling steps; one peer-reviewed study supports polyglutamic acid stabilization of Cas9 RNP nanoparticles and modified repair templates as a way to improve editing efficiency and reduce toxicity in clinically relevant primary cells, but this should be used only when the protocol is intentionally based on that study[7].
• Measure editing efficiency at the DNA level by PCR amplification of the target locus followed by Sanger-based indel analysis or amplicon sequencing, and measure functional knockout by flow-cytometric loss of the encoded protein when an antibody-based assay is available[3][4][6][8][9][10][11].
• Use mock-electroporated cells, Cas9-only or guide-only controls when reported, and non-targeting-guide controls to distinguish editing-dependent effects from electroporation, RNP exposure, culture, activation, infection, or expansion effects[4][6][8][10][11].
• Assess viability and recovery alongside editing efficiency because primary immune-cell protocols report editing in the context of cell fitness, recovery, or preservation of immune-cell function after RNP delivery[4][6][7][8][10][11].
• Design guide RNAs against the target locus and include a non-targeting or safe-harbor/control guide when possible; assemble Cas9 and guide RNA as RNP immediately before delivery, following the cell-type-specific RNP format used in the selected source protocol[3][4][6][8][9][10][11].
• Prepare cells according to the matching immune-cell protocol: activate or culture T cells as required by the chosen T-cell method, maintain resting B cells before nucleofection when following the B-cell study, expand NK cells before site-specific insertion workflows, or purify CD14+ monocytes before monocyte editing[3][4][8][9][10][11].
• Deliver the preassembled Cas9 RNP into primary immune cells by electroporation or nucleofection using the program and buffer conditions validated for the specific cell type; because instrument programs and buffer formulations differ across studies, use only the exact settings reported for the chosen cell type rather than transferring settings between T cells, B cells, NK cells, monocytes, and ILC/myeloid cells[3][4][6][8][9][10][11].
• For knockout experiments, culture edited cells after RNP delivery until protein loss or indel formation can be measured; reported studies analyzed editing by flow cytometry and/or DNA amplicon analysis after recovery, expansion, differentiation, infection, or stimulation steps appropriate to the immune-cell type[4][6][8][9][10][11].
• For knock-in experiments, provide a donor repair template only in workflows where donor delivery was tested, such as Cas9 RNP with HDR donor in primary human T cells, non-viral donor targeting in T cells, modified repair templates with Cas9 RNP, or Cas9 RNP plus AAV in primary NK cells[3][5][7][9].
• Do not add unsupported enhancers or handling steps; one peer-reviewed study supports polyglutamic acid stabilization of Cas9 RNP nanoparticles and modified repair templates as a way to improve editing efficiency and reduce toxicity in clinically relevant primary cells, but this should be used only when the protocol is intentionally based on that study[7].
• Measure editing efficiency at the DNA level by PCR amplification of the target locus followed by Sanger-based indel analysis or amplicon sequencing, and measure functional knockout by flow-cytometric loss of the encoded protein when an antibody-based assay is available[3][4][6][8][9][10][11].
• Use mock-electroporated cells, Cas9-only or guide-only controls when reported, and non-targeting-guide controls to distinguish editing-dependent effects from electroporation, RNP exposure, culture, activation, infection, or expansion effects[4][6][8][10][11].
• Assess viability and recovery alongside editing efficiency because primary immune-cell protocols report editing in the context of cell fitness, recovery, or preservation of immune-cell function after RNP delivery[4][6][7][8][10][11].
Troubleshooting
Low protein knockout despite RNP delivery.
Possible cause:Guide RNA performance or target accessibility is insufficient in the selected primary immune cell.
Literature-supported solution:
Test additional guide RNAs and verify editing by DNA-level indel analysis before concluding that the gene is resistant to knockout[3][4][6][8][10][11].
Poor viability after editing.
Possible cause:Electroporation/nucleofection stress or donor/RNP toxicity.
Literature-supported solution:
Optimize delivery conditions within the validated cell-type-specific protocol and consider polymer-stabilized RNP only when following the Nguyen et al.
Workflow[4][7][8][10][11].
Immune activation after RNP editing.
Possible cause:In vitro-transcribed guide RNA can activate RIG-I and induce type I interferon signaling.
Literature-supported solution:
Use synthetic or chemically modified guide RNA formats supported by the selected protocol rather than IVT guide RNA[10][12].
Knock-in is inefficient.
Possible cause:Donor delivery and repair-template design are limiting.
Literature-supported solution:
Use knock-in workflows that have been directly tested in primary immune cells, such as Cas9 RNP with donor template in human T cells or Cas9 RNP plus AAV donor in primary NK cells[3][5][7][9].
Verweise:
- [1]. Jinek M, et al. A programmable dual-RNA-guided DNA endonuclease in adaptive bacterial immunity. Science. 2012;337(6096):816-821. [Content Brief]
- [2]. Cong L, Ran FA, Cox D, Lin S, Barretto R, Habib N, et al. Multiplex genome engineering using CRISPR/Cas systems. Science. 2013;339(6121):819-823. [Content Brief]
- [3]. Schumann K, Lin S, Boyer E, Simeonov DR, Subramaniam M, Gate RE, et al. Generation of knock-in primary human T cells using Cas9 ribonucleoproteins. Proc Natl Acad Sci U S A. 2015;112(33):10437-10442. [Content Brief]
- [4]. Seki A, et al. Optimized RNP transfection for highly efficient CRISPR/Cas9-mediated gene knockout in primary T cells. J Exp Med. 2018;215(3):985-997. [Content Brief]
- [5]. Roth TL, Puig-Saus C, Yu R, Shifrut E, Carnevale J, Li PJ, et al. Reprogramming human T cell function and specificity with non-viral genome targeting. Nature. 2018;559(7714):405-409. [Content Brief]
- [6]. Oh SA, et al. Ribonucleoprotein transfection for CRISPR/Cas9-mediated gene knockout in primary T cells. Curr Protoc Immunol. 2019;124(1):e69. [Content Brief]
- [7]. Nguyen DN, Roth TL, Li PJ, Chen PA, Apathy R, Mamedov MR, et al. Polymer-stabilized Cas9 nanoparticles and modified repair templates increase genome editing efficiency. Nat Biotechnol. 2020;38(1):44-49. [Content Brief]
- [8]. Riggan L, Hildreth AD, Rolot M, Wong YY, Satyadi W, Sun R, et al. CRISPR-Cas9 ribonucleoprotein-mediated genomic editing in mature primary innate immune cells. Cell Rep. 2020;31(7):107651. [Content Brief]
- [9]. Kararoudi MN, Nagai Y, Elmas E, de Souza Fernandes Pereira M, Ali SA, Imus PH, et al. Optimization and validation of CAR transduction into human primary natural killer cells using CRISPR and AAV. Cell Rep Methods. 2022;2(7):100236. [Content Brief]
- [10]. Freund EC, Lock JY, Oh J, Maculins T, Delamarre L, Bohlen CJ, et al. Efficient gene knockout in primary human and murine myeloid cells by non-viral delivery of CRISPR-Cas9. J Exp Med. 2020;217(7):e20191692. [Content Brief]
- [11]. Akidil E, Wissing J, Dobberstein N, Ciloglu N, Arnold N, Höfig I, et al. Highly efficient CRISPR-Cas9-mediated gene knockout in primary human B cells for functional genetic studies of Epstein-Barr virus infection. PLoS Pathog. 2021;17(4):e1009117. [Content Brief]
- [12]. Wienert B, et al. In vitro-transcribed guide RNAs trigger an innate immune response via the RIG-I pathway. PLoS Biol. 2018;16(7):e2005840. [Content Brief]
LinkedIn
Researchgate
Instagram
X
Facebook
WhatsApp
Reddit
Mail